The flowers his friend gave him will die unless every day.
A. watering
B. watered
C. is watered
D. waters
网友回答
A. watering
(答案→)B. watered
C. is watered
D. waters
解析：考查省略形式。unless后面应该加的完整部分是they are watered，前后主语一致都是flowers，这时可以省掉主语和be动词，这样只剩下watered。所以选B。