Half of your brain stays alert and prepared for danger when you sleep in a new place, a study has revealed. This phenomenon is often __26__ to as the "first-night-effect". Researchers from Brown university found that a network in the left hemisphere of the brain "remained more active" than the network in the right side of the brain. Playing sounds into the right ears (stimulating the left hemisphere) of __27__ was more likely to wake them up than if the noises were played into their left ear.
It was __28__ observed that the left side of the brain was more active during deep sleep. When the researchers repeated the laboratory experiment on the second and third nights they found the left hemisphere could not be stimulated in the same way during deep sleep. The researchers explained that the study demonstrated when we are in a __29__ environment the brain partly remains alert so that humans can defend themselves against any __30__ danger.
The researchers believe this is the first time that the "first-night-effect" of different brain states has been __31__ in humans. It isn't, however, the first time it has ever been seen. Some animal __32__ also display this phenomenon. For example, dolphins, as well as other __33__ animals, shut down one hemisphere of the brain when they go to sleep. A previous study noted that dolphins always __34__ control their breathing. Without keeping the brain active while sleeping, they would probably drown. But, as the human study suggest, another reason for dolphins keeping their eyes open during sleep is that they can look out for __35__ while asleep. It also keeps their physiological processes working.
A) classified
B) consciously
C) dramatically
D) exotic
E) identified
F) inherent
G) marine
H) novel
I) potential
J) predators
K) referred
L) species
M) specifically
N) varieties
O) volunteers
答案解析：
根据“This phenomenon is often...to as the 'first - night - effect'”，可知这里考查固定搭配“be referred to as”(被称作，被称为)，所以选K。
根据语境，这里是说把声音播放进“志愿者”的右耳比播放进左耳更有可能唤醒他们，“volunteers”(志愿者)符合语境，所以选O。
根据“observed that the left side of the brain was more active during deep sleep”，这里需要一个副词来修饰“observed”，“specifically”(特别地，具体地)符合，表示特别观察到左脑在深度睡眠期间更活跃，所以选M。
根据“when we are in a...environment the brain partly remains alert”，结合前文提到在新的地方睡觉会出现“first - night - effect”，可知是在“新的”环境中大脑会部分保持警觉，“novel”(新的)符合，所以选H。
根据“defend themselves against any...danger”，可知是要防御任何“潜在的”危险，“potential”(潜在的)符合，所以选I。
根据“the 'first - night - effect' of different brain states has been...in humans”，可知这里是说这种大脑不同状态的“first - night - effect”在人类身上被“确认”，“identified”(确认，识别)符合，所以题选E。
根据“Some animal...also display this phenomenon”，可知这里说的是一些动物“物种”也表现出这种现象，“species”(物种)符合，所以选L。
根据“dolphins, as well as other...animals”，海豚属于海洋动物，这里说和其他“海洋”动物一样，“marine”(海洋的)符合，所以选G。
根据“dolphins always...control their breathing”，可知海豚总是“有意识地”控制呼吸，“consciously”(有意识地)符合，所以选B。
根据“they can look out for...while asleep”，结合语境可知是睡着的时候留意“捕食者”，“predators”(捕食者)符合，所以选J。
