When processing an internal table with the statement LOOP AT itab... ENDLOOP, the system variable that contains the current row number is sy-tabix. The sy-tabix variable is a predefined field of the system structure sy that holds the index or the row number of the current line in an internal table loop. The sy-tabix variable is initialized with the value 1 for the first loop pass and is incremented by 1 for each subsequent loop pass. The sy-tabix variable can be used to access or modify the current line of the internal table using the index access12.
References: 1: LOOP AT itab - ABAP Keyword Documentation - SAP Online Help 2: System Fields - ABAP Keyword Documentation - SAP Online Help

In a RESTful Application Programming (RAP) application, you can bind a CDS view to create a value help in the following objects:
* Data model view: A data model view is a CDS view that defines the data structure and the associations of an entity in the RAP application. You can use the annotation @Consumption.valueHelpDefinition to bind a value help provider CDS view to an element of the data model view. The value help provider CDS view must contain the key fields of the value help entity and the fields that are displayed in the value help dialog. The value help annotation specifies the entity name, the element name, and optionally the additional binding conditions for the value help provider1.
* Metadata Extension: A metadata extension is a CDS view that extends the metadata of another CDS view without changing its data structure. You can use the annotation @MetadataExtension.extendView to specify the target CDS view that you want to extend. You can then use the same annotation
@Consumption.valueHelpDefinition to bind a value help provider CDS view to an element of the target CDS view. The metadata extension allows you to add value help definitions to existing CDS views without modifying them2.
* Projection View: A projection view is a CDS view that defines the projection of another CDS view.
You can use the annotation @AbapCatalog.sqlViewType: #PROJECTION to specify that the CDS view is a projection view. You can then use the same annotation @Consumption.valueHelpDefinition to bind a value help provider CDS view to an element of the projection view. The projection view allows you to add value help definitions to projected elements of another CDS view3.
You cannot bind a value help provider CDS view to a behavior definition or a service definition, because these objects do not define the data structure or the metadata of an entity in the RAP application. A behavior definition defines the behavior and the validation rules of an entity, such as the create, read, update, and delete (CRUD) operations, the draft handling, the authorization checks, and the side effects4. A service definition defines the service exposure and the service binding of an entity, such as the protocol, the version, the namespace, and the service name5.
References: 1: Value Help with Additional Binding | SAP Help Portal 2: Metadata Extensions - ABAP Keyword Documentation 3: Projection Views - ABAP Keyword Documentation 4: Behavior Definition - ABAP Keyword Documentation 5: Service Definition - ABAP Keyword Documentation

A generic internal table type is a table type that does not define all the attributes of an internal table in the ABAP Dictionary; it leaves some of these attributes undefined. A table type is generic in the following cases1:
* You have selected Index Table or Not Specified as the access type.
* You have not specified a table key or specified an incomplete table key.
* You have specified a generic secondary table key.
A generic table type can be used only for typing formal parameters or field symbols. A generic table type cannot be used for defining data objects or constants2.
Therefore, the correct answer is B. INDEX TABLE, which is a generic table type that does not specify the access type or the table key. The other options are not generic table types, because:
* A. SORTED TABLE is a table type that specifies the access type as sorted and the table key as a unique or non-unique primary key3.
* C. STANDARD TABLE is a table type that specifies the access type as standard and the table key as a non-unique standard key that consists of all the fields of the table row in the order in which they are defined4.
* D. HASHED TABLE is a table type that specifies the access type as hashed and the table key as a unique primary key5.
References: 1: Generic Table Types - ABAP Dictionary - SAP Online Help 2: Generic ABAP Types - ABAP Keyword Documentation - SAP Online Help 3: Sorted Tables - ABAP Keyword Documentation - SAP Online Help 4: Standard Tables - ABAP Keyword Documentation - SAP Online Help 5: Hashed Tables - ABAP Keyword Documentation - SAP Online Help

The internal table type that allows both unique and non-unique keys is the standard table. A standard table has an internal linear index that can be used to access the table entries. The key of a standard table is always non- unique, which means that the table can contain duplicate entries. However, the system does not check the uniqueness of the key when inserting new entries, so the programmer can ensure that the key is unique by using appropriate logic. A standard table can be accessed either by using the table index or the key, but the response time for key access is proportional to the table size.
The other two internal table types, sorted and hashed, do not allow non-unique keys. A sorted table is filled in sorted order according to the defined table key, which must be unique. A sorted table can be accessed either by using the table index or the key, but the response time for key access is logarithmically proportional to the table size. A hashed table can only be accessed by using a unique key, which must be specified when declaring the table. A hashed table has no index, and the response time for key access is constant, regardless of the table size.
References: Internal Tables - ABAP Keyword Documentation, SAP ABAP: Types Of Internal Table Declaration - dan852.com