Considering the recentdangerous situatio
题型：选择题
问题：
Considering the recent dangerous situation, safety locks are required to be equipped to prevent
houses from being ____. [ ]
A. broken in
B. broken into
C. broken up
D. broken off
题型：选择题
Considering the recent dangerous situation, safety locks are required to be equipped to prevent
houses from being ____. [ ]
A. broken in
B. broken into
C. broken up
D. broken off
Pu可由铀239(
U）经过n次β衰变而产生，则n为（ ）