A：it
B：is
C：are
—Guang'an is a beautiful city, isn't it?
—Yes. There are about two _______ visitors here every week.
从前的黄土高原有茫茫的林海和无边的草原，而今却成了荒山秃岭，其主要原因是（ ）
最近法国某著名攀爬运动员在张家界成功徒手攀爬百龙天梯井架，引起众人的关注，下列有关攀爬活动说法不正确的是（ ）
