.
______ his homework, he went on to preview the next lesson.
| A．Doing | B．To do | C．done | D．Having done |
According to the psychoanalyst Sigmund Freud, wisdom comes from the _____ of maturity.
| A．fulfillment | B．achievement | C．establishment | D．accomplishment |
This is the _____ piano on which the composer created some of his greatest works.
| A．actual | B．genuine | C．real | D．original |
He was deep in thought with his eyes_____ on the ceiling.
| A．fixed | B．fixing | C．fix | D．to be fixing |
The car was completely _____ and the driver seriously injured.
| A．broken off | B．taken off | C．written off | D．picked up |
Although the causes of cancer_____, we do not yet have any practical way to prevent it.
| A．are being uncovered | B．have been uncovering | C．are uncovering | D．have uncovered |