a drop in the bucket 沧海一粟 ; 九牛一毛 ; 微不足道

Drop in the bucket 九牛一毛 ; 水桶的一滴

a drop in a bucket 沧海一粟

drop-bottom bucket 活低式料斗 ; 底卸式铲斗

double-door drop-bottom bucket 对开底卸料斗

drop bottom bucket 活底式料斗

single-door drop-bottom bucket 单底开式加料斗

drop p in the bucket 沧海一粟