【单选题】两个阻值分别为4Ω和12Ω的电阻并联在一起,等效电阻为
【单选题】The magician picked three persons______ from the audience and asked them to help him with the performance.
【单选题】The magician picked out several persons ______ from the audience and asked them to help him with the performance.
【判断题】富含氢的脂肪、蛋白质为底物时吸收的氧气多,RQ大于1。( )
【单选题】母乳喂养的婴幼儿添加辅食,从第几个月开始最好: