Dear Sir, 31. A. I’m writing for you about bad situation, which is affecting the lake near my school. B. I’m writing to you about bad situation, which is affecting the lake near my school. C. I was writing to you about bad situation, which is affecting the lake near my school. D. I’m writing to you to bad situation, which is affecting the lake near my school. 32. A. As you know, the lake near my school is very beautiful. B. As you know, the lake near my school is very beautifully. C. As you know, the lake near my school are very beautiful. D. As you known, the lake near my school is very beautiful. 33. A. However, it has become polluting. B. However, it has became polluted. C. However, it has become polluted. D. However, it have become polluted. 34. A. People have used electricity to catching fish. B. People have used electricity to caught fish. C. People have used electricity to catch fish. D. People have use electricity