Many people can not learn any lessons from the mistakes____they get hurt somehow.

Sorry indeed I______ to your birthday party if …—Forget it I know you were out on business

31. To our surprise, they decided to________their differences and try to face the coming global problems together.

依次填入下面一段文字横线处的语句，衔接最恰当的一组是（ ）科学研究表明， ， 。 ， ， 。 ，强身且做不到，又何谈强国①在一些大城市，人们不得不压抑户外健身的热情②整个民族的身体健康状况出现下滑③人们不呼吸新鲜空气几分钟都难以存活④中小学甚至开始削减长跑等户外体育运动课程和考试项目⑤由于空气质量的恶化⑥人们不吃饭可以活7到20天，不喝水可以活3到7天

At first he did not realize that he had succeeded in making a computer that ran on solar power(太阳能). “Realize” in the sentence means “___________”