The challenge is not one of expansion. _______, the rapid growth in enrollment over the last 40 years has come to an end.
正确答案： D
本题解析：
本题考查介词词组的词义辨析。四个词组分别表示“因此”、“务必”、“相比之下”和“相反”之意。
The wounded soldiers would recover quickly if they were well ________.
_______ at all is worth doing well.