曹操在官渡、仓亭大破袁绍后未乘胜追击，却退兵的原因何在？
参考答案：
刘备乘虚进攻许昌
After having gone _______ far, Tom did not want to turn back. [ ]
A. enough
B. much
C. such
D. that
简述现代康复对截肢手术的观点。
