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.