设椭圆$\frac{x^2}{6}+\frac{y^2}{2}=1$和双曲线$\frac{x^2}{3}-y^2=1$的公共焦点为$F_1,F_2$，$P$是两曲线的一个公共点，则$\cos \angle F_{1}P{F}_2$的值等于（       ）

在静止的电梯里某人站在测力计上，测力计的弹簧被压缩l，当电梯以大小为g的加速度匀加速上升时，下列说法正确的是（   ）

从右栏方框中选出能填入左栏空白处的最佳选项，其中有两项是多余的。

W: Can I help you?
M: Yes. ____ 
W: Do you like the white one?
M: No, ____ That yellow one looks nice.
W: Yes. Please try it on.
M: Oh, it' s too long for me.____ 
W: Certainly. Here you are.
M: Good! This is nice.____ 
W: 30 dollars.
M:____ 

阅读短文，判断正误。

    My father has nice sungIasses. They’re five yuan. They‘re very cheap. My mother has a pretty scarf. I have an umbrella. It’s 50 yuan. It’s very expensive