選B,支持tomwalkson ACDE都是拿過去師生比的變化來試圖加強此argument,可是從(However, any recession will not reduce~)可知,本題的argument關心的是未來的蕭條發生時師生比的變化,而過去跟未來不同之處,最重要的一點,就在於多了一條legal requirement,因為有這一條新的法規的制定,改變了大環境,我們便無法拿過去的理由來預測未來的變化,所以ACDE無法加強此一argument。而B即使選它需要我們多推一步,但不管如何它發生的時間總是在未來(精確的說總在legal requirement實行之後),因此可以加強此一argument。
Cause it's free of charge, the student will stay constant or increase but will not decrease, plus that the ratio is higher now than that is in recession period, so student stay constant or increase and teacher must also stay constant and increase to keep the ratio unchanged.