【题目】One of my old pals called me last night. Believe it or not，it's________ five years since we last met.
A.at length
B.at most
C.at least
D.at last

【答案】C
【解析】A．at length最后；B．at most至多；C．at least至少；D．at last最后；句意：昨晚一位老朋友打电话给我，信不信由你，我们至少五年没见面了。根据句意，故选C。