50. What is the second paragraph mainly about?
(A) The high cost of desalinating seawater.
(B) The major chemical characteristics of seawater.
(C) The urgent need to turn seawater into fresh water.
(D) The amount of energy produced in the desalination of seawater.

46. Which of the following statements is true about West Nile? (A) Its symptoms usually appear within two weeks. (B) It is spread through air and water in tropical areas. (C) Over 20% of people who contract it will suffer severe symptoms. (D) It comes from direct human contact with birds infected with the virus.

47. What did Dallas County do to fight off West Nile? (A) They sprayed pesticide from the air. (B) They asked citizens to stay away from dead birds. (C) They encouraged citizens to get vaccinations. (D) They drained the swimming pools in the county.

48. Which of the following is a reason why Dallas was hit most seriously in the U.S. in 2012? (A) The increasing population in Texas raised the risk of contracting the disease. (B) The government did not issue a warning about the disease in time. (C) The residents worried about the county’s decision and action. (D) The weather of the previous winter was not as cold as usual.

49. Which of the following is closest in meaning to “arid” in the first paragraph? (A) Occupied. (B) Isolated. (C) Dry. (D) Remote.

51. According to the passage, which of the following statements is true? (A) Mixing salt with water is not as easy as removing salt from seawater. (B) Desalinating seawater may kill some sea creatures and disturb the food chain. (C) Covering 70% of the Earth, the ocean has always satisfied human needs for water. (D) The increasing population in Saudi Arabia has resulted in shortages of fresh water.

52. Which of the following best describes the author’s attitude toward the future of desalination? (A) Amazed. (B) Doubtful. (C) Conservative. (D) Hopeful.

53. Which of the following titles best describes the main idea of this passage? (A) The Origin of Lullabies (B) The Functions of Lullabies (C) Threatening Lullabies (D) Sleep-Inducing Lullabies

54. Which of the following is closest in meaning to the word “undertones” in the first paragraph? (A) Consequences. (B) Vocals. (C) Whispers. (D) Messages.

55. What does the author use to support the idea that lullabies can have a soothing effect? (A) Research reports. (B) Examples found in history. (C) Stories of caretakers. (D) The author’s personal experiences.

56. According to this passage, which of the following statements is true? (A) Scary lullabies better help babies fall asleep. (B) Mothers prefer to sing lullabies with a joyful melody. (C) Lullabies comfort not only the baby but also the mother. (D) Babies react to both the music and the lyrics of lullabies.