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  3. It’s a good idea to apply sunscreen before heading to the beach if you don’t want to burn. But for marine animals like whales, t

It’s a good idea to apply sunscreen before heading to the beach if you don’t want to burn. But for marine animals like whales, t

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问题     It’s a good idea to apply sunscreen before heading to the beach if you don’t want to burn. But for marine animals like whales, they don’t have that【C1】______ Species like sperm whales can spend up to six hours at the ocean’s surface in between dives,【C2】______ in the sunlight. So how do they protect themselves from a serious case of sunburn?
    It turns out that their bodies have a similar defense【C3】______ against the sun’s UV radiation as people. Blue whales—which have the lightest skin color of the three species—tan during their summer stay before【C4】______ back to their northern feeding grounds. Sperm whales don’t tan. They can receive an "overdose" of UV radiation during their hours at the ocean’s surface, and they have proteins that【C5】______ protect their cells from UV damage. This process is【C6】______ to how human bodies produce antioxidants in response to molecules that can cause a lot of genetic and cellular damage. And fin whales escape sun damage thanks to their high levels of melanin—a dark substance in the skin to protect humans from UV radiation.
    Older whales and whales with less【C7】______ of melanin in their skin—like blue whales—had the greatest level of damage in their mtDNA. Fin whales, which had the greatest amount of melanin, had the least amount of mtDNA damage.
    Now that the ozone layer that shields Earth from UV radiation is gradually【C8】______ it’s important to know what the consequences are for whales and dolphins, especially for【C9】______ or endangered species. Although it’s difficult to tell what causes many of these skin conditions, UV damage is one cause. Even though whales have【C10】______ defenses to UV radiation, high exposure can still be harmful.
A) similar B) diminishing C) liability D) migrating
E) mutual F) mechanism G) effectively H) jerking
I) instantaneously J) vulnerable K) content L) baking
M) inherent N) perspective O) option
【C1】
选项
答案O
解析 空格在指示代词that之后，应为名词。that所指与上一句内容有关，指“去沙滩之前先涂上防晒霜”。此处应选择option，表示海洋动物“没有那样的选择”。mechanism通常用于指事物本身内在的机制，不适宜用于指代“涂防晒霜”，故排除。
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