50、B ____。Pressure on the optic nerve may cause blindness in the right or left halve s of both eyes or in the inner or outer halves of both eyes. Detachment of the r etina from the interior of the eyeball causes blindness by allowing the retina t o drift to the bottom of the eye out of range of the image formed by the lens; p ermanent correction usually requires surgery. Introduction Principles Defects Weakness Blindness
51、Environmental Impacts of Energy Production All primary energy sources that are ***nomic will be required if the world is to avoid energy starvation. The world’s needs for e(51)____ energy have been met successively by wood, coal and oil. As these sources decline in importance o(52)____ approach depletion, natural gas, nuclear power, solar and other ’alternative’ energy sources are expected to m(53)____ an increasing fraction of total demand. The production and use of energy can h(54 )____ a significant effect on the environment. The environmental consequences of the use of some energy sources c ould conceivably b***me so great t(55)____they could limit growth in energy con sumption. On the other hand, meeting energy needs for ***nomic development and s(56)____well-being may require that some environmental impcts be accepted. Environmental impact assessments are being used increasingly I(57)____ dec ision-making by national authorities r(58)____ for selecting appropriate energy options or energy mixes. The impacts of energy production may be of short durati on, long lasting, or irreversible. They may be of l(59)____or global concern, and may involve trans-boundary issues of international significance; they may af fect different communities, p(60)____ groups and countries in different ways. Th ey may be detrimental or beneficial. The nuclear industry has taken a leading ro le in addressing systematically both short- and long-term issues.
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答案：
1 D 2 B 3 A 4 B 5 B 6 D 7 B 8 D 9 C 10 C 11 A 12 C 13 A 14 D
15 C 16 C 17 C 18 A 19 B 20 B 21 C 22 A 23 C 24 B 25 A 26 D 27 C 28 D 29 B 30 A 31 C 32 C 33 B 34 B 35 C 36 B 37 C 38 A 39 D 40 B 41 B 42 A 43 C 44 B 45 A 46 Introuction 47 Principles 48 Defects 49 Weakness
50 Blindness 51 energy 52 or 53 meet 54 have 55 that 56 social 57 in 58 responsible
59 local 60 population