26. The explorer of America is Columbus.
27. Nobody in Nam's class is fatter than him. (S1 + am/is/are + adj-er + than + S2)
28. She has been doing her homework for 1 hour. (HTHT)
29. It's very interesting to swim in the sea.

30. It was such a difficult exercise that I couldn't do it.
31. She asked if I was cooking at the moment.
32. This problem can be solved.
33. They have been playing tennis since 2003. (HTHT)
34. I haven't seen him for 2 weeks. (HTHT)
35. In spite of his broken legs, he managed to get out the burn.
36. The last time someone saw Mary was her birthday.
37. If he had had enough money, he would have bought the laptop. (QKHT)
38. Daisy apologized for having not phoned me earlier.
39. It is said that he had been saved.

26. The explorer of America is Columbus.

27. Nobody in Nam's class is fatter than him.

28. She has been doing her homework for 1 hour.

29. It's very interesting to swim in the sea.

30. It was such a difficult exercise that I couldn't do it.

31. She asked if I was cooking at the moment.

32. This problem can be solved.

33. They have been playing tennis since 2003.

34. I haven't seen him for 2 weeks.

35. In spite of his broken legs, he managed to get out the burn.

36. The last time someone saw Mary was her birthday.

37. If he had had enough money, he would have bought the laptop. (QKHT)

38. Daisy apologized for having not phoned me earlier.

39. It is said that he had been saved.