修改病句。 
1．太平洋绿龟长大后体重约在一百五十公斤左右。
                                                                                                                                                   
2．新中国成立后，科学家已经为治理黄河描绘了方案。
                                                                                                                                                   
3．飞机设计师研制了具有优良性能的各种飞机。  
                                                                                                                                                   
4．通过本单元的学习，使全班同学明白了环保的重要性。