题干
Next put all the ingredients in a big bowl and ________.
A：mix up them
B：mix them up
C：mix it up
D：mix up it
答案(点此获取答案解析）
B
Next put all the ingredients in a big bowl and ________.
A：mix up them
B：mix them up
C：mix it up
D：mix up it
均为单位向量，且
，
，则
的最大值为