问题补充：
People love the convenience of bottled water, but if they the problem it causes, they try carrying water in a reusable steel container instead of plastic.
A. realized; will
B. had realized; will
C. realized; would
D. have realized; would
答案：
A. realized; will
B. had realized; will
(答案→)C. realized; would
D. have realized; would
解析：C 考察虚拟语气。句义：人们喜欢瓶装水的便利，但如果他们意识到瓶装水会导致的问题，他们就会使用可循环的铁罐代替塑料瓶来装水。If虚拟句表示对现在的虚拟假设。故C正确。
