A:旅游业是旅游活动的媒介
B:旅游业是一种劳动密集型的第三产业
C:旅游业是”无烟工业”
D:旅游业是一种综合性的行业
Sam has got a bike. He goes to school by bike. Amy hasn't got a bike. Her father has got a car. She goes to school in her father's car. Daming hasn't got a bike. He goes to school by bus.
—Skating on the ice is ______.
①董事会是公司的执行机构
②监事会是公司的监督机构
③经理等是公司的执行机构
④董事会是公司的最高权力机构
复数z=2-i2+i(i为虚数单位)在复平面内对应的点所在象限为( )
读黄河流域图和黄河下游“地上河”示意图,回答问题。