①在水平木板上铺白纸，把弹簧的一端固定在O点，过O画一条标记线OD，弹簧的另一端拴两条细绳套；用两把弹簧秤互成角度拉细绳套，使弹簧的另一端沿OD拉至C点，如图甲所示．用铅笔描下C点的位置和两条细绳的方向，记录两弹簧秤的读数分别为F_A与F_B，其中B弹簧称的读数F_B=____N；用刻度尺测出此时弹簧的长度为10cm，通过计算得出弹簧的拉力F=____N；可以判断F_A与F_B互成的角度为____．

②根据力的图示，作出F_A和F_B，如图乙所示．请你根据力的图示，在图乙中作出F_A与F_B的合力F′____．

③比较力F′与F的大小和方向，得出的结论是：在实验误差范围内，____．

____

A: Paul! What are you going to do this evening?

B:____What about you?

A: I plan to see the Beijing Opera.____

B: Yes. I'd like to go with you.

(A moment later ...)

A: Paul, do you like the Beijing Opera?

B:____I feel bored when I see it.

A:____I think it's interesting. Maybe you don't know how to enjoy the opera. That's the problem.

B：____

函数$y=\sqrt{9-{\left(x-5\right)}^2}$的图象上存在不同的三点到原点的距离构成等比数列，则以下不可能成为该等比数列的公比的数是（   ）