_______ is certain that practice makes perfect.
| A．What | B．It | C．There | D．Anything |
―Who are those people walking along the street with banners?
―A group _______ itself the League for Global Environment Protection.
| A．calling | B．called | C．being called | D．is called |
_____ human beings live in great numbers, the waters are very likely to become contaminated.
| A．That | B．Where | C．Even if | D．Though |
_____ I admit that the problems are difficult , I don’t agree that they cannot be solved.
| A．While | B．Suppose | C．Because | D．as though |
It was found that although the girl could perceive things with her fingers, this ability ceased _____ her hands were wet.
| A．the moment when | B．the moment | C．in that moment | D．before |
______ you understand this rule, you’ll have no further difficulty.
| A．while | B．Once | C．Though | D．Unless |