Question 19 is based on the recording you have just heard.

听力原文

    In 1984, the World Chess Championship was called off abruptly due to the withered frame of a player who was competing for the title. He wasn’t alone in experiencing extreme physical effects of the game. Elite players can reportedly burn up to an absurd six thousand calories in one day.

    Does that mean that thinking harder is a simple route to losing weight? Well, (19) [when the body is at rest, we know that the brain uses up a startling 20% to 25% of the body’s overall energy.] This level of utilization actually makes the brain the most energy-expensive organ in the body, and yet it makes up only 2% of the body’s weight overall.

    So the more we put this organ to work, the more calories we’ll burn? Technically, the answer is yes, for cognitively difficult tasks. What counts as a “difficult” mental task varies between individuals. But generally, it could be described as something that “the brain cannot solve easily using previously learned routines, or tasks that change the conditions continuously”. However, deep thinking will not burn off the calories gained from eating a sugary snack. Because in relation to the brain’s huge overall energy usage, which is devoted to a multitude of tasks, the energy required just to think harder is actually comparatively tiny. (20) [We are unconscious of most of what uses up the brain’s energy—a lot of that activity is unrelated to conscious activities like learning how to sing or play the guitar.]

    (21) [The brain is able to allocate blood and thus energy to particular regions that are being active at that point. But the overall energy availability in the brain is thought to be constant.] So, while there might be significant increases in energy use at localized regions of the brain when we perform difficult cognitive tasks, when it comes to the whole brain’s energy budget overall, these activities don’t significantly alter it.

    So why did the chess champion grow too skinny to compete in his chess competition? The general consensus is that it mostly comes down to stress and reduced food consumption, not mental exhaustion. Keeping your body pumped up for action for long periods of time is very energy-demanding. If you can’t eat as often or as much as you can or would normally, then you might lose weight.

19. What do we learn about the brain when the body is at rest?（关于身体休息时的大脑活动，我们可以了解到什么？）

解析：D。录音前半部分提到，当身体处于休息状态时，大脑消耗的能量占身体耗能的20%-25%。D项与此内容相符，其中almost a quarter对应录音中的20% to 25%，the body’s total energy对应录音中的the body’s overall energy，故D项为正确答案。

错项排除：A项利用录音中出现的deep thinking设置干扰，但录音中只提到了从含糖零食中所摄取的能量是不能仅靠深度思考来完全消耗掉的，没有将大脑休息时和深度思考时的能量消耗作对比，故A项错误。录音中提到了休息时（at rest）大脑消耗的能量占比，还提到了大脑的能量消耗并不会因为一些活动而产生显著（significantly）变化，B项利用inactive与at rest、noticeably与significantly的对应来设置干扰，属于细节拼凑，故排除。录音中提到，虽然大脑总共消耗的能量巨大，但仅通过努力思考所消耗的能量相比之下其实很少，由此可知，仅靠脑力活动来减肥或保持身材并不现实，故C项排除。