问题
选择题
You can’t be ______ when you camp _____ a high altitude, ________ the air is thin.
A．enough careful; at; which
B．too careful; at; where
C．careful enough; on;at which
D．too careful; on; that
答案
答案：B
第一空考查短语：can’t… too 再什么也不为过，第二空考查短语：at a high altitude以很高的海拔，第三空考查定语从句，先行词为a high altitude，从句中缺少地点状语。所以选B。