根据中文意思完成英语句子，每空一词。
【小题1】令人惊讶的是，一些科学发现是偶然发现的。
Surprisingly, some scientific discoveries were made _____ _____.
【小题2】我将亲手制作卡片，感谢母亲为我所做的一切。
I’ll make a card myself to be _____ _____ my mother for what she has done for me.
【小题3】中国母亲河长江，是世界第三长河。
The Yangtze River, the mother river of China, is the _____ _____ river in the world.
【小题4】在大学毕业之后，我们终于有机会出国旅游了。
After _____ _____ university, we finally got the chance to travel abroad.
【小题5】近四十年来，中国发生了巨大的变化。
Great changes have _____ _____ in China in the past forty years.