49 According to this passage, when are people most likely interested in the study of drought?
(A)In times of war.
(B)After an earthquake.
(C)Right in the midst of water shortage.
(D)At the time when both trees and people grow complacent.

When provided with continuous nourishment營養；養分, trees, like people, grow “complacent自滿的，自鳴得意的”—the word tree-ring環 scientists use to describe trees like those on the floor of the Colorado River Valley, whose roots tap into接进 thick厚的, 粗的, 稠的 reservoirs水庫；蓄水池 of moist soil.

Complacent自滿的，自鳴得意的 trees aren’t much use for learning about climate history, because they pack包裹, 一群 on wide new rings環 of wood even in dry years.

To find trees that feel the same climatic pulses脈衝、搏動, 跳動 as the river, trees whose rings widen變寬, 擴大 and narrow from year to year with the river itself, scientists have to climb up the steep不平緩的, （斜坡）陡的, rocky slopes斜坡 above the valley and look for gnarled多瘤節的, ugly trees, the kind that loggers樵夫 ignore.

For some reason such “sensitive” trees seem to live longer than the complacent自滿的，自鳴得意的 ones. “Maybe you can get too much of a good thing,” says Dave Meko, a tree-ring scientist who has been studying the climate history of the western United States for decades. Tree-ring fieldwork實地考察；野外研究 is hardly expensive, but during the relatively相對 wet 1980s and early ’90s, Meko found it difficult to raise even the modest funds基金, 支助, 投资 for his work. “You don’t generate interest to study drought unless除非 you’re in a drought,” he says.