The flowers his friend gave him will die unless every day.
A. watered
B. watering
C. water
D. to water
网友回答
(答案→)A. watered
B. watering
C. water
D. to water
解析：因“花”与“浇水”之间为被动关系，所以选过去分词。其实，unless watered可视为unless they are watered之省略。类似的还有：Unless changed. this law will make life difficult for farmers. 这项法令除非进行修改，否则将给农民的生活造成困难。