I will have a holiday next week and I can't decide what to do. I have a lot of work to do 1 and this would be a good chance 2. But I don't like 3 the holiday in such a way.I can work at home all the rest of the year.

    Last year I went 4 to the mountains. 5 there was beautiful， but it is too cold this time of a year. And it's really6 far to go for a short holiday. I decide 7 this isn't a good time to8the mountains.But I9to go somewhere else.Perhaps this would be a good chance to go to the beach（海滨）.I like to go for walks10the seashore 11the warm sunshine and watch the water. It's only eight miles away and I could get there 12about two hours. After thinking it13，I am sure that this is a 14time for the seashore than15.

    Oh， here is a 16from Jim. He 17 he is going to his house in the mountains for the18，and he19me to go with him.20 giving it some more thought， I wrote back to Jim and thanked him for that.

爱因斯坦根据广义相对论预言了引力波的存在。上世纪70年代，一些科学家提出用激光干涉方法探测引力波。上世纪90年代，探测需要的技术条件逐渐趋于成熟，并于1999年建成“激光干涉引力波天文台”（LIGO），后经过多次技术升级，终于在2015年9月首次探测到引力波。引力波的发现过程反映了(   )

①真理是具体的有条件的      ②追求真理是一个过程

③实践是认识发展的动力      ④改造世界是认识的目的