Some scientists think it came after an unexpected incident when a huge rock from space hit the earth and put too much dust into the air.

有些科学家认为恐龙灭绝是发生在一件意外事故之后，当时宇宙间一块巨石击中地球因而在空气中扬起太多的尘土。

The clock struck five. This silent mental debate had occupied her whole afternoon. Perhaps it would not have ended now but for an unexpected incident—the entry of her brother Louis.

时钟敲了五下。这场无声的思想辩论占据了她整个下午。如果不是因为她哥哥路易斯的到来，也许它不会现在结束。