Many students listened to the lecture, but I wondered how much work they took________.[ ]

下列各句中，没有语病的一句是 ( )

Do you mind him _______ TV all the time—Of course. I am busy with everything and can’t get a helping hand.

_____ the city’s public school system should be opento the children of migrant workers has become the focus of discussion.

Research has been limited to ____ production profits,rather than ____ that GM foods are safe.