You know,maybe I'll put together some photos of Grandpa as a welcome present.
我说,或许我把爷爷的一些照片组合起来,作为欢迎他的一份礼物。
The second marks the arrival of transverse vibrations which travel more slowly and arrive several minutes after the first.
然后记录下的是横向波的到达,横向波比纵向波传播得慢,在纵向波到达几分钟后才能到达。