问题
选择题
Radium salts，which have been found to ______ in bones，give rise to bone cancer.
A．pile up
B．build up
C．keep up
D．pull up
答案
答案：B
考查短语辨析。build up(="accumulate)" 积累。pile up 堆积。keep up 保持，维持。 pull up 停车。根据句意选B。