按要求改写句子。     

1．鲁滨孙非常喜欢航海和冒险。     

改为反问句：                                                                            

2．鲁滨孙把捕到的活山羊畜养起来。     

改为“被”字句：____                                                                             

3．鲁滨孙救了这个逃跑的野人。     

改为双重否定句：____                                                                              

4．他在荒无人烟的小岛上居然生活了二十多年。     

改为设问句：                                                                                        

使蛋白质从水溶液中析出而又不变质的方法是[ ]

A．过滤

B．加入硫酸铵溶液 　

C．加入福尔马林溶液

D．分液