能携带氨基酸到蛋白质合成场所的核酸是() ["tRNA","mRNA","rRNA","hnRNA","DNA"]
已知A物重力的大小P=20N,B物重力的大小Q=30N,滑轮C、D不计质量,并略去各处摩擦,则绳水平段的拉力为:() ["30N","20N","16N","24N"]
能参与蛋白质合成场所结构的核酸是() ["tRNA","mRNA","rRNA","hnRNA","DNA"]
洞室作业时,遇不良地质构造或易塌方地段,有害气体逸出及地下涌水等突发事件,应()。 ["立即停工,并撤至安全地点","查清楚突发事件后再撤离","经领导批准后撤离","以上都不对"]
上消化道出血病因诊断的首选检查措施为() ["X线钡餐造影检查","选择性动脉造影","内镜检查","化验检查","吞线试验"]
金属风管的连接方式有()连接、()连接。