根据首字母提示完成句子。

1. A s___________ line is the shortest distance between two points.

2. He is completely s_______ in his business dealings.

3. There was no wind that day. The smoke rose s________  upward.

4. He went s________  home after school.

5. The first question he asked me was quite s________

6点钟后，时针和分针第一次重叠的钟面时间是6：30．______．