—Oh, dear! I forgot my best friend’s birthday.
— Better keep it in mind next year.
| A．You did? | B．Why not? |
| C．Never mind. | D．No problem. |
I ________ the living room．Look，it is clean．
A．clean B．am cleaning C．have cleaned
The children ________ at the table when their mother cooked in the kitchen．
A．wait B．are waiting C．were waiting
--How many times has Chang’eⅠ ________ the Moon？
--Only once．It went there last year．
A．go to B．gone to C．been to
We have learned English ________ six years．
A．since B．for C．on
I ________ this English book since I came to Hefei No．28 High School．
A．have bought B．bought C．have had