21. Every minute should he made full use of_______our lessons. ?
| A．studying | B．to study | C．study | D．being studied? |
Though I am improving my study, I still have a long way to go __________ some of my classmates.
| A．to compare with | B．to compare to |
| C．comparing with | D．compared with |
The traffic on the main streets has a longer green signal than __________ on the small ones.
| A．one | B．this | C．that | D．it |
Alice received an invitation from her boss，__________ came as a surprise.
| A．it | B．that | C．which | D．he |
Paper is __________ great Chinese contribution to human civilization.
| A．a | B．the | C．不填 | D．an |
Read this story，__________ you will realize that not everything can be bought with money.
| A．or | B．and | C．but | D．so |