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.

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.

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.

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.

3.A charged particle at rest is released in a region of uniform electric field in the y direction and uniform magnetic field in the z direction. Which of the following statements is not correct? (A) The motion of the particle in the y direction is periodic. (B) In average, the particle moves with a constant speed in the x direction. (C) The kinetic energy of the particle increases with time. (D) The magnetic field does no work on the particle.

4. For an ideal electric quadruple, what is the relation between the electric field strength E and the distance r in the far field? (A)(B) (C) (D)

5.Consider two long parallel wires of radius a, separated by a distance d. If d□ a, find the capacitance per unit length. (A)(B) (C) (D)

6. In the static case, consider an interface between the free space and a perfect conductor with some charges on the surface. Which of the following statements is not correct? (A) The electric field in the free space near the surface is proportional to the surface charge density. (B) There is no electric field in the conductor. (C) The surface charge would experience no electric force. (D) The electric potcntial is the same in the conductor, even near sharp edges.