birds-----their wings rapidly as they fly ona hit b knock c beat d strike

问题描述:

birds-----their wings rapidly as they fly on
a hit b knock c beat d strike

C
鸟儿在飞的时候总是快速地拍动翅膀
beat有 某物不停地拍动 这种意思,可以指鸟儿的翅膀的拍动

d

C 表示有节奏的敲打