( )1.(2012年甘肃白银)The old man sold all his collections ________ the children in hospital.
A.to help B.help
C.helped D.helps
( )2.(2012年黑龙江黑河)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年黑龙江绥化)It's going to rain.Don't forget ________an umbrella.
A.to take B.taking
C.to make
( )4.(2012年湖南常德)It's nice of you ________ me with my maths!
A.help B.helping
C.to help
