下列各组式子中，属于同类项的是(  )

    My mother is very nice. She is a ____ （work） in a clothes store. She usually gets up at 6: 30. Then she cooks breakfast for me. After ____（have） a bowl of porridge and some broccoli, she goes to work at 7: 30. There ____ （be）usually many people in her clothes store. So she is very busy.

    My mother's work in the morning is over at 11: 45, and starts again at 1: 30 in the afternoon. So she has to have lunch in the store. Her work in the afternoon ____ (end) at 5: 30, and she goes home at 6: 30. Then she has dinner with ____ (we）at home. After dinner we watch TV together.

下面关于生态系统的说法中,错误的是(  )

区分蚯蚓的前端与后端，通常依据（　　）

已知：${\sin }^{2}30°+{\sin }^{2}90°+{\sin }^{2}150°=\frac{3}{2},{\sin }^{2}5°+{\sin }^{2}65°+{\sin }^{2}125°=\frac{3}{2}$  ;

通过观察上述两等式的规律，请你写出一般性的命题，并给出的证明.