A:why she was crying
B:why was she crying
C:why she is crying
D:why is she crying
定义:A={b,c,a},B={c},A∪B={a,b,c},若M={﹣1},N={0,1,﹣1},则M∪N={____}.
【透视人民代表大会制度】认真阅读下图,回答问题: