什么是熔和比？
参考答案：
指被熔化的母材在焊缝金属中所占的百分比。
临床上怀疑全身多发转移瘤首选的影像学检查方法为（）
A.ECT
B.超声
C.CT
D.MRI
E.X线平片
Sally took a photo of her friends while they_____computer games.
A．play
B．are playing
C．have played
D．were playing
