A:①②
B:②③
C:③④
D:①③
A. Have you got an email from Tom?
B. What did your mother have for lunch?
C. Does Lingling like hamburgers?
D. He says sandwiches are delicious.
E. I had eggs and milk.
如图所示,小华被蹦床弹起,向上运动的过程中,其机械能的变化是( )