People thinking about the origin of language for the first time usually arrive at the conc
【C1】
A.must be
B.must have been
C.ought to be
D.should be
B
解析:musthavedone用来表示对过去某动作的肯定推测,例如:HemusthavebeentoEngland,forheknowssomuchaboutthatcountry.他一定去过英国,因为他了解那么多有关那个国家的事情。