【单选题】Many birds and insects can build ______ nests to provide shelter for their young.
【多选题】两块平行金属板带灯亮异种电荷,要使两极板间的电压加倍,可采用的办法有
【单选题】Only after her mother came to help her for the first few months _____ to begin her project.
【单选题】Many birds and insects can build ______ nests to provide shelter for their young.