单选题 34. Under controlled conditions, orange trees that were raised from seedlings and exposed to double the normal concentration of carbon dioxide grew to triple their normal size. These dramatic results demonstrate that the rising global concentration of atmospheric carbon dioxide will prove a boon to world agriculture.
Which of the following, if true, would help support the conclusion above? ______

A、 Produce from plants that have undergone growth surges as a result of increases in atmospheric carbon dioxide is less nutritious per ounce than produce from plants that have grown at a normal rate.
B、 The orange trees in the study produced three times the normal amount of fruit.
C、 Some soil nutrients that affect plant growth are depleted as the amount of atmospheric carbon dioxide increases.
D、 The variety of orange tree used in the study is comparatively short and stocky in size.
E、 As the amount of carbon dioxide increases, vegetation that competes with agricultural crops also surges in growth.

【正确答案】 B

【答案解析】 B：在原文橘子树长得更大这一基础上，又增加了果实产量更高这一证据，提升了二氧化碳对农业有帮助的可能性，属于“列举证据”，正确。
A：全球二氧化碳上升的条件下产生的农作物营养含量反而不高，这对农业来说是坏事，削弱原文，不选。
C：土壤营养流失对农业发展是坏事，削弱原文，不选。
D：橘子树本身是否矮小与本题无关。本题关注的是二氧化碳带来的变化，与植物本来的大小无关，不选。
E：二氧化碳含量上升，农业面临的竞争也在加剧，说明这对农业未必是好事，削弱原文，不选。