Dưới đây là những câu hoàn thành cho từng trường hợp mà bạn đã cung cấp:

47. Unlike most teenagers, watching documentaries is one of my interests. (keen)
**I am keen on watching documentaries, unlike most teenagers.**

48. In the middle of our lunch, there was a knock at the door.
**When we were having lunch, there was a knock at the door.**

49. It is ages since I last visited my cousin’s house.
**The last time I visited my cousin’s house was ages ago.**

50. I am excited about playing a prank on my sister with my enormous plastic spider.
**I couldn’t wait to play a prank on my sister with my enormous plastic spider.**

Hy vọng những câu này sẽ giúp bạn!