连词成句。
（1） keep , trees, us, can, cool  (.)
                                     .
（2） is, fun, planting, trees (.)
                                    .
（3）the, should, look, we, young, after , trees(.)
                                      
（4） good, planting, for, is, trees ,us (.)
                                     
（5） will, plant, more, I, trees (.)