請依下文回答第 21 題至第 25 題
We know that a lack of sleep will prevent your brain from being able to make new memories, so it’s __21__  withoutsleep the memory inbox of the brain shuts down and you can’t commit new experiences to memory. So thosenew __22__ informational emails are just bounced. You can’t essentially make and create those newmemories. We also know that a lack of sleep will __23__ an increased development of a toxic protein in thebrain and that is associated with Alzheimer’s disease. It is during deep sleep at night __24__ a sewage systemwithin the brain starts to wash away this toxic protein. So if you’re not getting __25__ sleep each and everynight, more of that Alzheimer’s-related protein will build up.
【題組】21
(A) as to
(B) as if
(C) as usual
(D) as for