A new theory ( ) before it can be put into practice.(本题分数:2 分.)

问题描述:

A new theory ( ) before it can be put into practice.(本题分数:2 分.)
A new theory ( ) before it can be put into practice.(本题分数:2 分.)
A、 must be tested
B、 be tested
C、 can be tested
D、 to be tested

A new theory ( A ) before it can be put into practice.(本题分数:2 分.)
A、 must be tested
B、 be tested
C、 can be tested
D、 to be tested