The monument was built in honor of the explorer who was believed＿＿the big river.
| A．to have discovered | B．to have been discovered |
| C．to be discovered | D．having been discovered |
—Tom lost his job last week．
—___he is wandering in the street these days．
| A．No doubt | B．No way | C．No wonder | D．No problem |
The witnesses(证人) of the accident said that the lorry _______ very fast at the crossroads when the accident happened.
| A．is traveling | B．had travelled |
| C．was to travel | D．was travelling |
._____ nothing is doing ill.
| A．Do | B．To do | C．Doing | D．Does |
Our monitor talks about Mars as if he ______ a scientist.
| A．is | B．were | C．be | D．had been |
Your floor is dirty. It needs _______.
| A．clean | B．to clean | C．cleaning | D．cleaned |