while this tough meat is being cooked,more water should----it

题目

while this tough meat is being cooked,more water should----it
a be added to b add to c be adding to d be added up to
选哪个 请说明理由

答案

选 A,因为这里要用被动,所以排除了B与C,而D的意思是总共达多少的意思.