( )①Mary,help yourself to some fish.②Can I get you some rice?③I can help myself,thank you.

问题描述:

( )①Mary,help yourself to some fish.②Can I get you some rice?③I can help myself,thank you.
④Thank you.
A.③②①④ B.①②④③ C.④②③① D.①④②③

应该是D为什么?