I will visit you tomorrow________I’m too busy．
A．unless
B．if
C．because
Sorry, I _______ to help you at nine. I was busy at that time.
| A．won’t come | B．can’t come | C．didn’t come | D．shouldn’t come |
His sister _______ from home for a long time.
| A．has left | B．has been away | C．left | D．will leave |
To improve his riding skills, he spends _______ an hour a day practicing riding.
| A．at last | B．at least | C．at once | D．at all |
Jim said he _______ dinner. He was quite full.
| A．had had | B．was having | C．had | D．had eaten |
Is _______ hard for you to finish the work on time?
| A．that | B．it | C．what | D．which |