宋徽宗亲自主持完成的两部著作分别是:()
A、《宣和画谱》和《宣和图谱》
B、《宣和画谱》和《宣和书谱》
C、《宣和图谱》和《宣和书谱》
D、《宣和诗谱》和《宣和书谱》
参考答案:B
下列物质中,暂未计入北京市空气质量日报的监测空气污染指数的物质是( )
A.二氧化硫
B.二氧化碳
C.二氧化氮
D.一氧化碳
A firm in a perfectly competitive market will tend to expand its output as long as:()
A. its marginal revenue is positive.
B. the market price is greater than the marginal cost.
C. its marginal revenue is greater than the market price.