题目

做测定空气中氧气含量的实验时，若红磷的量不足，所测得氧气的体积分数_______ (填“偏大”、“偏小”或“不变”)。 答案：偏小 I’m        the blackboard, but I can’t        any words. A. looking, see            B. looking at, see                 C. seeing, look at