【单选题】Trees are useful to man in three very important ways: they provide him with wood and other products they give him shade and they help to pr droughts (干旱) and floods. Unfortunately, man has not re...
【单选题】Trees are useful to man in three very important ways: they provide him with wood and other products they give him shade and they help to pr droughts (干旱) and floods. Unfortunately, man has not re...