15. When Madam Curie did the experiment again, she was more careful where she _____ a mistake.
| A．made | B．has made | C．was making | D．had made |
Sometimes they may play to passers-by in the street or subway so that they can earn some______ money for themselves or to pay for their instruments.
| A．certain | B．extra | C．various | D．unusual |
The band about 1970, but happily they reunited in the mid1980s.
| A．broke up | B．broke down | C．broke out | D．broke in |
As a result these endangered animals may even .
| A．die away | B．die down | C．die out | D．die off |
I’m protecting myself mosquitoes.
| A．from | B．in | C．on | D．at |
What must be done if wildlife protection is?
| A．success | B．succeed | C．successful | D．to succeed |