单项选择题
A.Economics is B.Economice is C.Economics are D.Economics have been
A.has received B.ought to have received C.couldn't have received D.shouldn't have received
A.as poor, if not poorer than, his sister B.poor as his sister' s if not poorer C.as poor as, if not poorer than, his sister' s D.as poor, if not poorer than, his sister' s