For a Grammar, the Terminals are separate from the Non Terminals. This means they are disjoint. Hence if they are not disjoint the grammar will be meaningless.
So, (A) is correct.
LHS of a grammar must contain a Non Terminal. If it is only a terminal, then the grammar will be meaningless.
So, (B) is correct.
No need to look at (C) It must be correct, as just two can not be correct. Either One or All can be correct.
So, (D) is correct.