——_________ should your robot need_________ batteries?
——Every two months.
| A．How soon, to be changed | B．How long, to change |
| C．How much, change | D．How often, to change |
When the teacher asks him, he always ____.
| A．keep silent | B．keep silently |
| C．keeps silent | D．keeps silenty |
Mr. Li makes me ____, because it is bad for my health.
| A．don’t smoke | B．not smoke |
| C．not smoking | D．not to smoke |
Tom didn’t go hiking with his classmates ____ his illness.
| A．because | B．because of | C．as | D．since |
Your mother prepared delicious food for us yesterday. Please say thanks ____ her.
| A．for | B．to | C．with | D．of |
Helen is 15 years old, and Joan is 15, too. So Helen is ____ Joan.
| A．as big as | B．as older as |
| C．as old as | D．so old as |