下列属于明北京商业区的是() ["东大市","西大市","鼓楼一带","前门大栅栏","宣武门"]
精子获能的主要部位是() ["卵巢","子宫颈","阴道","子宫和输卵管","阴道后穹隆"]
以学为中心的课件设计原则有哪些?
雌激素的生理功能是() ["促进卵泡和子宫发育","降低子宫对缩宫素的敏感性","减少输卵管上皮细胞的活动","使阴道上皮细胞内糖原减少","促进体内水钠排泄"]
下列属于元大都内著名的市场的是() ["顺城门内的羊角市,相当于西四","枢密院角市,相当于东四","钟鼓楼及其以西的斜街一带","齐化门附近的市场","东岳庙附近的市场"]
1m3自然状态下的某种材料,质量为2100kg,孔隙体积占25%,其密度是()g/cm3。