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  3. Researchers led by New York University neuroscientist Joseph LeDoux recently claimed to be the first scientists to erase a singl

Researchers led by New York University neuroscientist Joseph LeDoux recently claimed to be the first scientists to erase a singl

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问题     Researchers led by New York University neuroscientist Joseph LeDoux recently claimed to be the first scientists to erase a single memory. Working with rats, LeDoux’s team first【B1】______the animals to fear both a beep and a siren【B2】______giving them an electric shock every time either of the tones sounded. Then LeDoux gave half the rats the drug U0126, which is known to【B3】______with memory storage, and replayed the beep【B4】______electric shocks.
    A day later, when LeDoux【B5】______back both tones to the rats, the animals that hadn’t been given the drug were still fearful of both sounds.【B6】______the rats that had been given the memory-blocking drug weren’t【B7】______of the beep, which they had last heard while【B8】______the influence of U0126.
    【B9】______how U0126 exerts its amnesiac effect is【B10】______, but it may block the synthesis of proteins that help strengthen【B11】______between neurons and establish memories. The opportunity for erasure【B12】______during the act of retrieving a memory, because that’s【B13】______the memory is being updated and【B14】______again for long-term storage. " Only those memories that are activated are【B15】______," LeDoux says.
    Drugs like U0126 may someday【B16】______sufferers of traumatic memories. A small group of human studies have been done on a drug called propranolol, which blocks the action of stress neurotransmitters that help【B17】______memories in the brain, but LeDoux’s work shows the【B18】______for greater precision. " You might be able to【B19】______the traumatic impact of memories in people," says LeDoux. " The good news is you wouldn’t be【B20】______off their memory bank. "
【B12】
选项 A、starts
B、occurs
C、arises
D、happens
答案B
解析 动词辨析题。本句讨论记忆阻隔药物发挥作用的时机和条件。由句意可知，当某个记忆检索行为发生的时候，该段记忆易被消除。由此可知正确答案应为[B]occurs“出现”，表示“记忆消除时机出现”。根据主谓搭配关系，易排除[A]starts“开始”，因为opportunity“时机”强调短暂性，瞬时性，没有明确的起终点，不能与starts搭配。[D]happens“发生”，则突出偶然性和出乎意料之意，也不符合文意，故排除。而[C]arises“出现”，虽表面意义相合，但该词多用于困难、问题等逐渐显现，因此也不符合原文意思，故排除。
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