Scientists believe native Americans arrived by crossing the land bridge that connected Siberia(西伯利亚)and more than 10，000 years ago．
| A．this is Alaska | B．Alaska is now | C．is now Alaska | D．what is now Alaska |
If I can help_______, I don't like working late into the night.
| A．so | B．that | C．it | D．them |
_______ is our belief that improvements in health care will lead to a stronger, more prosperous economy.
| A．As | B．That | C．This | D．It |
I’d appreciate ____ if you would like to teach me how to use the computer.
| A．that | B．it | C．this | D．you |
As the busiest woman in Norton,she made_________her duty to look after all the other people’s affairs in that town.
| A．this | B．that | C．one | D．it |
The chairman thought________necessary to invite Professor Smith to speak at the meeting .
| A．that | B．it | C．this | D．him |