【课堂练习】
( )1.(2012年白银)The old man sold all his collections ________ the children in hospital.
A.to help B.help
C.helped D.helps
( )2.(2012年黑河)The math problem is so hard.I really don't know________.
A.how to do it B.how to do
C.what to do it
( )3.(2012年绥化)It's going to rain.Don't forget ________an umbrella.
A.to take B.taking
C.to make
