A.....man never helps others without thinking of his own benefit

A:unselfish. B:selfishness. C:selfish. D:unselfishness

He has been very interested in doing research on........

.since he was at high school.

A:biology. B:biologically. C:biologist. D:biological

A sense of.......makes a girl beautiful.

A:humor. B:humorist. C:humorless. D:humorous

Tim is too young (join)..........the army