翻译下列句子：
1. 他的父母结婚二十年了。
___________________________________________
2. 她的丈夫过去很健康,现在偶尔他看上去不健康。
___________________________________________
3. 越来越多的人认识到我们必须尽力减少各种污染。
___________________________________________
4. 昨晚直到李雷做完作业他父母才回来。
___________________________________________
5. —最近你收到你父母的来信了吗？—是的。昨天收到一封。
___________________________________________
1. His parents have been married for twenty years.
2. Her husband used to be very healthy but now he looks unhealthy from time to time.
3. More and more people have realized /realize that we must try to reduce all kinds of pollution.
4. Li Lei's parents didn’t come back until he finished doing his homework.
5.—Have you heard from your parents recently?—Yes, I received a letter yesterday.
(答案不唯一)