The right answer is letter D. "Take your dirty dishes to the kitchen sink, please".
The sentence above is a full and polite one which expresses a clear course of actions a child couldn't question. In this respect, option A. is lacking because it is a exclamation expressing general disapproval; option B. comes ambiguous in its use of the reference "that" ; and C's "cleanup time" may come across as ambiguous in lack of too clear a context for the child.
