单词拼写(共5小题; 每小题1分, 满分5分)

根据首字母或汉语提示，在句子中填入适当的单词。

小题1:Bamboo grows up straight and thin, with b____ at the top.

小题2: He had attempted to rescue the _____（溺水的）man.

小题3:The i_____ of the computer marked the beginning of a new era.

小题4:A red light is usually a _____ (信号) of danger.

小题5:John is _____ (订婚) to Mary.

什么是售票时的定座情况？