1.(2013·全国Ⅰ，24)If we ________ now to protect the environment, we'll live to regret it.
A．hadn't acted B．haven't acted
C．don't act D．won't act
答案：C 本题考查动词时态。句意：如果我们不行动起来保护环境，我们会后悔的。根据主句的时态及从句中的now可知，条件从句要用一般现在时态，故C项正确。
2．(2013·全国Ⅰ，27)When I first met Bryan I didn't like him, but I ________ my mind.
A．have changed B．change
