John does important research _______ the best ways to help the old.
#48571
A
finds
B
finds
C
found
D
to find out
推荐题目
_____ the environment is important for human beings.
#50494
A
Take care of
B
Taking care of
C
Took care of
D
Take the care of
Don’t forget ______ the door when you leave.
#49672
A
close
B
closed
C
to close
D
closing
She looks very busy . I want to help her , but I don't know  ___________ .
#50250
A
what to do
B
what to do it
C
how to do
D
why to do