Scientists believe Native Americans arrived by crossing the land bridge that connected Siberia and _________ more than 10 000 years ago.
| A．this is Alaska | B．Alaska is now |
| C．is now Alaska | D．what is now Alaska |
I was_______ about it. I thought you were responsible and that’s why I scolded you. Please forgive me.
| A．curious | B．worried | C．particular | D．mistaken |
Every possible means ______to prevent the air pollution, but the sky is still not clear.
| A．are being used | B．have been used |
| C．has been used | D．had been used |
I have no _______ to the plan, so long as it would not cost too much.
| A．refusal | B．comment | C．idea | D．objection |
Don’t use words, expressions or phrases _____ only to people with specific knowledge.
| A．being known | B．having been known |
| C．to be known | D．known |
Scientists still wonder ______ cloning will help or harm us and _____ it is leading us.
| A．that; what | B．whether; where |
| C．if; that | D．whether; how |