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发布时间：2006-06-22 13:25     点击：

    (A) Ⅰ only

    (B) Ⅱ only

    (C) Ⅲ only

    (D) Ⅰand Ⅱ only

    (E) Ⅰand Ⅲ only

    26. The author implies that which of the following is the primary reason that degradation is as important as synthesis to the smooth operation of the carbon cycle?

    (A) Most of the polymers and organic compounds found in the plant kingdom are chemically unstable.

    (B) The synthesis of some organic material deprives life processes of an energy source.

    (C) Decomposition permits the recycling of carbon that would otherwise be fixed in certain substances.

    (D) Many organisms cannot use plants as a source of food, but can feed on bacteria and fungi.

    (E) Bacteria and fungi could not survive if some carbon compounds were not degraded.

    27. The author's contention about the importance of bacteria and fungi in the production of energy for life processes would be most clearly strengthened if which of the following were found to be true?

    (A) Both aerobes and anaerobes provide sources of energy through the decomposition of organic material.

    (B) Most compounds containing carbon are unavailable as energy sources except to some bacteria and fungi.

    (C) Bacteria and fungi break down inert material in ways that do not involve oxidation.

    (D) Many compounds remain inert, even in the presence of bacteria and fungi.

    (E) Bacteria and fungi assist in the synthesis of many organic compounds.

    28. SLUR:

    (A) avoid completely

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