下图是突触模式图。请据图回答：（[]内填序号）
右图中神经兴奋传递的方向是向（）（左／右），因为（）。
参考答案：左；神经递质只能由前膜释放作用于后膜
若取地球的半径为6371米，球面上两点A位于东经121°27'，北纬31°8'，B位于东经121°27'，北纬25°5'，则A、B两点的球面距离为______千米（结果精确到1千米）．
句型转换。
1. There're few students in the classroom. (改为反意疑问句)
There are few students in the classroom, _________?
2. She was having lunch at this time yesterday. (对画线部分提问)
_________ _________ she _________ at this time yesterday?
3. He read a storybook last night. (改为过去进行时)
He _________ _________ a storybook last night.
4. My son didn't come back home. I called him. (合并为一个由until引导的含时间状语从句的复合句)
_____________________________________________________________
5. His bag is full of sweets. (改为同义句)
His bag is _________ _________ sweets.
