C. Choose the best answer to complete the passage (选择最恰当的选项完成短文) (16分)
Have you ever wondered what happens inside your brain while you sleep? Every night, you experience__55__sleep cycles（睡眠周期）made up of light sleep, deep sleep and REM sleep—the dreaming stage（阶段）.Of these stages, deep sleep __56__most, as brain waves slow to their lowest level, activating(激活) the brain's waste-clearing glymphatic system(胶状淋巴系统).
Brain cells use energy to support thinking, learning, and studying. As a result, they produce harmful waste products that need to be removed（移除）. The glymphatic system flushes（冲洗）this __57__out with brain fluid (脑脊液), just like a built-in dishwasher. Danish scientist Maiken Nedergaard and her team uncovered（发现）what __58__this cleaning process（过程）.
Their research showed that a chemical called norepinephrine (NE) plays a central role in this process. In deep sleep, the brainstem releases（释放）small bursts of (一股) NE every 50 seconds. This makes tiny brain blood vessels shrink(收缩) and expand(扩张) repeatedly. As the volume（量）of blood shifts（变换） back and forth（来回）, it forces（迫使）brain fluid to circulate（循环）, __59__ mini pumps（泵）to sweep waste away. When you get enough high-quality sleep, norepinephrine(去甲肾上腺素) cleans your brain__60__. Yet lack of（缺乏）sleep stops this nightly clean-up, letting toxic（有毒的）waste increase.
To support this essential（重要的）brain maintenance（维护）, you need enough deep sleep. __61__a fixed（固定的）bedtime to regulate（调节）your body clock, avoid screens one hour before bed, and read to calm your mind. These simple __62__ keep your mind clear daily and protect long-term（长期的）brain health. So, give your brain the rest it needs and allow it to refresh（刷新）itself overnight.
55.A)unusualB)repeated（重复的）C)similar D)continuous
56.A)appears B)changes C)matters D)differs
57.A)rubbish B)oxygen（氧气）C)energy D)blood
58.A)drives（驱动） B)replaces C)blocks（堵塞）D)changes
59.A)looking like B)dealing with C)depending on D)acting as（充当...角色）
60.A)quickly B)thoroughly（彻底地）C)partly D)gently
61.A)Ignore（忽略） B)Create C)Follow D)Copy
62.A)rules B)tasks C)plans D)habits
