In a spors team each player has a clear role，and there are few______when members are uncertain of their roles.
| A．occasions | B．positions | C．chances | D．situations |
Some people have the idea_____ you can cross Canada in less than five days.
| A．what | B．that | C．which | D．when |
Only after her mother came to help her for the first few months ______ to begin her project.
| A．did she allow | B．had she allowed |
| C．was she allowed | D．is she allowed |
Thanks to Dr Yuan’s research, the UN has more tools in the battle to rid the world _____ hunger.
| A．of | B．on | C．off | D．at |
______ is even more important is that the earth cooled down, water began to appear on its surface.
| A．When | B．That | C．Which | D．What |
Jane _____ these families of chimps for many years and helped people understand how much they behave like humans.
| A．had studied | B．studied | C．studies | D．has studied |