题目

.It was so dark in the cinema that I could hardly ____ my friend.    A. turn out   B. bring out   C. call out   D. pick out 答案：D 解析: pick out 意为“认出，选出”。根据所提供的情景“It was so dark in the cinema”可判断出由于电影院里很黑，很难认出朋友。turn out意为“打扫,驱逐,使外倾,生产,起床,翻出,制造,关掉”；bring out意为“使显示,出版,生产,说出”；call out意为“出动,唤起,大声叫唤”。公比为2的等比数列{an} 的各项都是正数，且  a3a11=16，则a5=（ ）A．1B．2C．4D．8