He has worked __________ the maths problem for nearly an hour but he simply can't work it __________.
| A．on；at |
| B．on；out |
| C．at；up |
| D．for；out |
In the garden there are a lot of flowers ______ I don’t know the names.
| A．of which | B．from which | C．to which | D．about which |
I was greatly ______ at how he worked out the ______ problem in a creative way.
| A．amazed; confused | B．amazing; confusing |
| C．amazed; confusing | D．amazing; confused |
My painting won the first prize, _____ changed my plans for the future.
| A．which | B．where | C．that | D．what |
—It’s a little bit cold today, but you have sweat all over.
—Yes, I _______ around the city for almost three hours.
| A．have hiked | B．was hiking | C．am hiking | D．have been hiking |
The rate of unemployment in America after the worldwide economic crisis may be ______ reported earlier.
| A．as twice high as | B．twice as high as |
| C．as high twice as | D．as high as twice |