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
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