Question

(2013·成都一診)Parents are doing all they ________ to help their children achieve their ambitions.

A．shall	B．can
C．may	D．need

Answer 1

B

選B　考查情態動詞。句意：父母們在做他們力所能及的事來幫助他們的孩子實現他們的夙愿。完整形式為“Parents are doing all they can do to help their children achieve their ambitions.”其中they can do是定語從句，修飾先行詞all; to help  their children achieve their ambitions是目的狀語。由于主句中出現了實義動詞doing，所以省略了從句中的do。故答案為B。