(A) exceedingly
(B) paralyzed
(C) demolishes
(D) downtime
(E) brutal (F) strikes(G) predominant(H) plaguing(I) that(J) partly (K) presumptuously (L) malformedFFI, fatal familial insomnia, is an awful disease, the main symptom of which is the inability to sleep. First the ability to nap disappears, then the ability to get a full night’s sleep, until the patient cannot sleep at all. The syndrome usually ___11___ when the sufferer is in his or her late 50s, ordinarily lasts about a year, and always ends in death, as the name indicates.To make matters worse, so little about how it works is known to researchers after years of study. So far researchers have only figured out that in a patient with FFI, ___12___ proteins called prions attack the sufferer’s thalamus, a structure deep in the brain, and ___13___ a damaged thalamus interferes with sleep. But they don’t know why this happens, or how to stop it, or ease its ___14___ symptoms. Before FFI was investigated, most researchers didn’t even know the thalamus had anything to do with sleep. FFI is ___15___ rare, known in only 40 families worldwide. But in one respect, it’s a lot like the less serious kinds of insomnia ___16___ millions of people today: It’s pretty much a mystery.If we don’t know why we can’t sleep, it’s ___17___ because we don’t really know why we need to sleep in the first place. We know we miss it if we don’t have it. And we know that no matter how much we try to resist, sleep conquers us in the end. We have known for 50 years that we divide our slumber between periods of deep-wave sleep and what is called rapid eye movement (REM), when the brain is as active as when we are awake, but our voluntary muscles are ___18___ . Furthermore, we know all mammals and birds sleep. Fish, reptiles and insects all experience some kind of repose too.Yet all this ___19___ comes at a price. An animal must lie still for a great stretch of time, during which it is easy prey for predators. So what possibly is the payback for such risk? As the renowned sleep researcher Allan Rechtschaffen once said, “If sleep doesn’t serve an absolutely vital function, it is the greatest mistake evolution ever made.” Not surprisingly, the ___20___ theory of sleep is that the brain demands it.
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