10. - Can you show me your headmaster's office?
-_____But I don't know if he is in at the moment.
A. Go ahead B. You're welcome c. Of course not D. Sure
________ doesn’t seem to have been any difficulty solving the problem.
| A．There | B．It | C．He | D．That |
Joan had often heard ____ said that Marley had no money.
| A．one | B．it | C．once | D．her |
Carl Linnaeus made great contributions to ________ plant species.
| A．group | B．have grouped | C．grouping | D．been grouping |
He observed a stranger _______ around the store at 12 p.m. last night.
| A．to hang | B．hang | C．hanging | D．to be hanging |
Once ______ , the plan can’t be changed.
| A．begin | B．beginning | C．began | D．begun |