B and D. A is used in UPDATE operations. C is not a valid keyword.
A2:
A and D. A is valid. Wildcard characters are actually not required when you use LIKE; the search is effectively an equality test. B is invalid; NOT must precede LIKE. C is invalid; wildcards can be used with strings, not with numbers. D is valid; there is no limit to the number of wildcard characters that you can use in a search.
A3:
B. You use UPDATE when columns (as opposed to rows) are affected. A, DELETE, deletes entire rows. C, NULL, is not a statement; it represents no value and can be used with UPDATE to set a column to no value.
A4:
B. Primary keys may indeed be made up of more than one column. All the other statements are false.
