30. A. It will help solve the global food crisis.
31. D. It is still far from being sufficient.
32. D. They are not as natural as we believed.
33. A. He was wrongly imprisoned
34. A. The two victims’ identification
35. B. Many factors influence the accuracy of witness testimony.
36. slight
37. official
38. shrinking
39. plunge
40. decline
41. primary
42. heads
43. Poverty
44. Hampered by higher taxes and weak demand for its exports. Mexico's economy is seen only partially recovering this year.
45. Mexico has historically had high drop-out rates as poor families pull kids out of school to help put food on the table，
46. The nation's drop-out problem is just the latest bad news for the long-term competitiveness of the Mexican economy.