精品一区二区免费在线观看_国产精品久久久久久av福利软件_97成人精品区在线播放_国内成人精品一区

The professor could hardly find sufficient grounds _____his arguments in favor of the new theory.

A. to be based on     B. to base on   

C. which to base on    D. on which to base

The professor could hardly find sufficient grounds _____his arguments in favor of the new theory.

A. to be based on     B. to base on   

C. which to base on    D. on which to base

The professor could hardly find sufficient grounds _____his arguments in favor of the new theory.

The professor could hardly find sufficient grounds _____his arguments in favor of the new theory.

A．to be based on     B．to base on         C．which to base on    D．on which to base

The professor could hardly find sufficient grounds _____his arguments in favor of the new

theory.