Dogs___are usually quiet have started to bark.A.they B./ C.that请说明原因
问题描述：
Dogs___are usually quiet have started to bark.A.they B./ C.that请说明原因
答
C.that
从结构来看,此部分___are usually quiet 应该为定语从句,由于指物,做主语,用关系代词that