在疟疾流行的地区，很多孩子在感染疟疾几次后才对疟疾具有免疫力。显然，孩子的免疫系统在受到疟原虫的一次攻击后，只能产生微弱的反应，而必须被攻击多次后才能产生有效的免疫反应。
以下哪项如果为真，最严重地削弱了上面的假设？（）

beyond bottom brand break bitter blame breakthrough bill brain by21. I am sorry it’s ______ my power to make a final decision on the project.22. Every day the mother seems to be busy until 10’clock at night, ______which time the rest of the family have fallen asleep.23. You will not know whether it is ______ or sweet if you don’t taste it yourself.24. After a long debate the ______ was passed and it will become law next month.25. The judge laid the _________ for the accident on the driver of the car.26. You're so kind; thank you from the ________ of my heart.27. The students who do best in examination are not always those with the best _______.28. Coke and Pepsi are the most popular ________ of cold29. The industrial park is not a very comfortable place to work in--- few trees or grassy areas; no cafes for staff to visit during their _______.30. They've made a major ____________ in the treatment of cancer. It is a great discovery. 点击查看答案

今人看书，普遍过于浮泛，如蜻蜓点水，不若古人之沉潜把玩。这是因为现在需要看的东西太多了，没时间，只好一目十行，都是’知道了’.还有一点，五四以前，我们太尊信古人；五四以后，我们又太藐视古人。都想开天辟地，都是前无古人，写自己的书都来不及，哪还有心思抄别人的书？这段文字主要谈论的是（）。

A．古人看书沉潜把玩
B．今人看书过于浮泛的原因
C．今人为什么没有心思抄别人的书
D．时代要求我们不能像古人那样看书

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