问题
选择题
No one knows for sure when such a custom first _____.
A．came into power
B．came into being
C．came true
D．came out
答案
答案：B
考查词组辨析：A. came into power开始执政，B. came into being开始形成C. came true成为现实， D. came out出版，发行，句意是：没有人知道这种风俗是什么时候形成的。选B。