改错。

( ) 1. If I find a million dollars, I would keep it.                                      

                   A                    B                   C

( ) 2. If I had much money, I will travel to the moon.                             

                   A                           B                       C

( ) 3. I wish he will lend me his car.                                                      

                A          B    C

( ) 4. I wish I hadn't to work today.                                                      

                 A         B                   C

( ) 5. Please excuse Mary of being absent from the meeting.                    

                          A              B                      C

输送带在运行时为什么会跑偏？跑偏时应如何调整？如何防止跑偏？