下列关于文学常识的表述，不正确的一项（ ）

While working on the farm， the students ________ a good knowledge of plant life

17．The movie is to deucate people about environmental problems ______our planet.

We have to stay at home instead of goingfinishing because it is raining ________________.

﹣How often do you have a school trip this term﹣_____．Since several accidents happened to some schools，all the school outdoor activities have been asked to stop．