题目

—Are you worried about the coming exam?      —No, I think the more ________ you study, ________ mistakes you’ll make.A. careful, the less               B. careful, the fewer        C. carefully, the less             D. carefully, the fewer 答案：D袋中共有6个除了颜色外完全相同的球，其中有1个红球，2个白球和3个黑球，从袋中任取两球，两球颜色为一白一黑的概率等于（ ）A．B．C．D．