The post-World War II baby （） resulted in a 43 percent increase in the number of teenagers in the 1960s and 1970s.

单项选择题The police are trying to （） what really happened.

A．ascertain
B．assert
C．avert
D．ascribe

单项选择题When construction can begin depends on how soon the （） of the route is completed.

A．conviction
B．identity
C．orientation
D．survey