37. What is the main idea of this passage?
(A) What nature-lovers do to protect our earth.
(B) How a waterfall is formed.
(C) An introduction of some of the world’s most famous waterfalls.
(D) A tour of South and North America.

33. According to the passage, what is the main reason beavers build their homes in ponds? (A) They like to live with wetland plants and animals. (B) Water can help to protect them from various dangers. (C) Their feet will be hurt once they step on land. (D) They can only give birth to their babies in the water.

34. According to the passage, why are ponds and wetlands good for cleaning streams? (A) They act like filters. (B) They enable the moose to have a better life. (C) They can breed more plants than the land. (D) They can keep the wolves away from the beavers.

35. According to the passage, which of the following descriptions of a beaver is NOT correct? (A) Its eyesight is excellent. (B) Its rear feet look like duck feet. (C) It has a good sense of smell and of hearing. (D) It is bigger than a mouse in size.

36. According to the passage, why were many beavers killed in the last few hundred years? (A) They had greatly damaged human beings’ living environment. (B) They were thought of as evil creatures by many Europeans. (C) Their teeth were precious. (D) Their fur was very valuable.

38. According to the passage, how many days may an explorer spend climbing up and then getting back down Angel Falls? (A) Half day. (B) One and a half days. (C) Nine and a half days. (D) Eleven days.

39. Which of the following waterfalls can be seen from both Argentina and Brazil? (A) Iguazu Falls. (B) Angel Falls. (C) Niagara Falls. (D) Victoria Falls.

40. According to the passage, which of the following is NOT true? (A) Angel Falls is the tallest in the world. (B) Niagara Falls is the most famous waterfall in the world. (C) The Iguazu Falls is located in North America. (D) Victoria Falls is 108 meters high.

41. What can we infer from the passage? (A) Niagara Falls is not safe to visit. (B) The author thinks waterfalls are a spectacular form of natural beauty. (C) The best way to appreciate a waterfall is to read an encyclopedia. (D) The largest waterfall in the world lies in Asia.

1.Which of the following statements is not correct? (A)(B)(C)(D)

2.Which of the following statements is not correct? (A) A curl-less vector field can be expressed as the gradient of a scalar field. (B) A divergence-less vector field can be expressed as the curl of a vector feld. (C) A curl-lJess and divergence-less vector field is a constant vector field. (D) A smooth and rapidly decaying vector field can be expressed as the sum of a curl-less vector field and a divergence-less vector field.