He ______ have been nervous because he didn’t go straight in.

A. It is made up of more than 100 states.
B. Its members contain less than half the world’s population.
C. It is made up of dozens of African and Asian countries.
D. It came into being 52 years ago.

A. have a better understanding of the life of mosquitoes
B. prevent human beings from being bitten by mosquitoes
C. purify the environment
D. keep people alert