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Read the following passage and choose the most likely answer to each of the following questions.

    Teens and young adults often turn up the volume on their iPods or smartphones or stand near the speakers at concerts or nightclubs, all in the name of having a good time. Even if they realize this could be damaging to their hearing, what neither they nor their parents know is that this kind of behavior could be altering their brain function for life. A study in a 2018 issue of the journal eNeuro found that young adults with subtle hearing loss——a deficit that's so slight that they're not even aware of it (they reported they had normal hearing)——are placing demands on their brains that don't normally occur until later in life.
    In the study, researchers used functional magnetic resonance imaging scans (磁共振成像扫描) to monitor brain activity, while healthy men and women listened to various sentences that varied in their complexity and the demands required to process and understand them. Before performing the scans, the researchers tested the participants' hearing ability and found that some of them had subtle hearing deficits, but were still clinically in the normal range.
    What the researchers found is that listeners with poorer hearing had activity in the right hemisphere of the brain, which was surprising because usually the left hemisphere of the brain is completely responsible for regulating and managing speech and language comprehension. And the altered brain function was still the same no matter how simple or complex the sentence structure was.
    The good news is that the brain is an amazingly plastic organ, meaning it has the ability to change and adapt throughout life, explains Yune Lee, an assistant professor of chronic brain injury at Ohio State University. As people age, they begin to use more of their right frontal brain to process language, but "we don't usually see that in younger people," Lee explains. "That is worrisome because they start using up these resources too early in life. It's like withdrawing money from a retirement account too early; these resources need to be kept for later in life."
    The findings are especially significant, says Sarah Sydlowski, audiology director of a Hearing Implant Program, because "hearing involves hearing sound but also processing it and extracting meaning in the brain. Exposure to loud sound can cause clinical damage to 'synaptic ribbons'——the connections between the sensory cells in the inner ear and the hearing nerve. People with this damage suffer from 'hidden hearing loss' because often they will appear to have normal hearing on a standard hearing test, yet they may complain that they have difficulty understanding speech in noisy environments."
    The long-term concern is that a growing amount of evidence has shown a significant link between hearing loss and dementia. In fact, a review of studies in the June 2018 issue of Maturitas found that hearing damage at midlife is associated with a 50 percent higher risk of developing dementia later in life. The theory is "If you put all your energy into hearing, you drain cognitive resources that could be used for other things such as memory and attention," Lee says.
    If you suspect that you're struggling to hear clearly or process what you hear comfortably or accurately, get your hearing checked, including your ability to hear and understand speech against background noise, Sydlowski advises. The researchers don't recommend routine hearing checks for adults, but the American Speech-Language-Hearing Association calls for adults to be checked for hearing loss every decade through age 50, then every three years after that. The sooner you detect a hearing problem, the better; that way, you can take steps to handle it, whether that means modifying your environment to minimize distractions, adding protection for your hearing, doing auditory training (listening exercises) or considering a hearing device, Sydlowski says.

Which of the following is closest in meaning to the word "dementia" in Paragraph 6?（ ）

Nervous disorder.

Loss of cognition.

Physical disability.

Symptom of depression.

本题考查对第六段中dementia的词义理解。
定位到第六段，本段大意为“长期的担忧是越来越多的证据表明听力损失和dementia之间有着显著的联系。事实上，关于2018年6月出版的Maturitas杂志的一项研究的评述发现，中年时听力受损会将晚年患dementia的风险提高50%。这个理论是“如果你把所有的精力都放在听觉上，那么你会消耗掉一些认知资源，而这些资源可能会被用来做其他事情，比如记忆和注意力。”，可以推断，dementia应该是一种疾病，表现为“认知丧失”，关键词是cognition。故选择B选项。