To our surprise the stranger to be an old friend of my mother’s.A. turned outB. turned up

问题补充：

To our surprise the stranger to be an old friend of my mother’s.

A. turned out

B. turned up

C. set out

D. set up

答案：

(答案→)A. turned out

B. turned up

C. set out

D. set up

解析：turn out 意为“结果是，原来是”等；turn up 意为“找到，发现，出现，开大音量”等；set out 意为“开始，出发，陈述”等；set up 意为“设立，竖立，架起，升起，创(纪录)，提出”等。