单句改错。 (     )1. By the time we got outside , the bus has already left . A                         B          C          D (     )2. I'm sorry I have forgotten my purse at home . A                         B           C           D (     )3. Don't wake up him .  He is too tired . A              B               C     D (     )4. I am just late to school. A   B    C   D (     )5. Do you need a pen to write on ? A           B     C                  D ________ ________ ________ ________ ________