题目

The time restriction (限制) for retaking International English Language Testing System (IELTS) will be abolished (废除) on May 1,2007. “Instead of having to wait 90 days before retaking the test, candidates will be able to repeat the exam immediately,” announced the British Council, the IELTS organizer in China. A change in the way the test is administrated allowed IELTS to lift the retake restriction. “In the past, for a test which has over three administrations a month, repetition of test questions was unavoidable. It’s unfair if some candidates got easy scores by luckily remembe有a、b两份等质量的双氧水溶液，在a份中加入少量二氧化锰，下图是二者产生氧气的质量m与反应时间t的关系的图象，其中正确的是 （ ）A. A B. B C. C D. D