Although Uncle John was sick, he was ______ enough to hear and see everything around him.
A、clear
B、alert
C、swift
D、quick-witted
【正确答案】：B
【题目解析】：本题考查形容词词义辨析。A.clear：清晰地，清楚的；B.alert:警觉的，警惕的；C.swift:快的，迅速的；D.quick-witted:机智灵敏的。根据题意，“尽管约翰叔叔病了，可他还是足够警惕的听清和看清周围事物。"B最符合题意。答案为B。
