根据句意,用所给动词的适当形式填空。
小题1:The teacher told us that the earth       (travel) around the sun.
小题2:Trees and grass play an important part in _______ (help) improve our environment．
小题3:Many trees___________(plant) in my hometown every year.
小题4:CCTV is starting a project _________( call ) “Looking for the most beautiful country teachers.”
小题5:We are talking about where ___________(spend ) our coming winter holiday.