The flowers his friend gave him will die unless ___ every day.
A.watered B.watering
C.water D.to water
The flowers his friend gave him will die unless ___ every day.
A.watered B.watering
C.water D.to water
A
unless后接省略形式。flowers和water之间是关系要用被动语态。同时unless从句的主语与主句的主语相同,常常省略其相同成分,故选A项,表示被动。动词-ing形式表示主动;不定式常用作目的状语。