【题目】One-third of the area _____ covered with trees. About seventy percent of the trees _____ been planted recently.
A.is; have
B.is; has
C.are; have
D.are; has

【答案】A
【解析】句意：这个地方三分之一被树覆盖，70%的树是最近种的。第一个句子主语是area是不可数名词，动词用单数；第二个句子主语是trees是可数名词，动词用复数。故选A。