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。Bamboo grows up straight and thin, with b____ at the top.
He had attempted to rescue the _____（溺水的）man.
The i_____ of the computer marked the beginning of a new era.
A red light is usually a _____ (信号) of danger.
John is _____ (订婚) to Mary.