合并下列句子
问题描述：
合并下列句子
1.He dropped a coin.He walk across the street(when)
2.He boiled the wather.He drank the water(before)
答
1.He dropped a coin when he walked across the street.He dropped a coin when walking across the street.2.He boiled the water before he drank it.He boiled the water before drinking it.