入冬以来,全国多地多次发生雾霾天气,能见度不足20 m。在这样的恶劣天气中,甲、乙两汽车在一条平直的公路上行驶,当两车同时行驶到同一位置时,两车
（10分）维生素C又称抗坏血酸，广泛存在于水果、蔬菜中，属于外源性维生素，人体不能自身合成，必须从食物中摄取。其化学式为C6H8O6，相对分子量
如图所示，在纪念抗日战争胜利70周年阅兵仪式中，某直升飞机在地面上空某高度A位置处于静止状态待命，要求该机10时56分40秒由静止状态沿水平方向
A volcanic eruption in Iceland has sent ash across northern Europe. Airlines have stopped or changed the flights across the Atlantic Ocean, leaving airport hundreds of passengers stuck in airport. Gri
某养鸡场自制电热孵化器用来孵小鸡。孵化器电阻丝的阻值为22 Ω，额定电压为220 V, 把它接在家庭电路中。 求：⑴工作时通过孵化器的电流； ⑵ 孵化
已知||=3，||=2，＜0，则的值等于（ ）A.5或－5 B.1或－1 C.5或1 D.－5或－1
阅读下面的短文，请根据短文后的要求答题（注意问题后的字数要求） [1] Do you ever wish you were as thin as a model or as strong as your favorite football player? Maybe you
_____ from heart trouble for years, Professor White has to take some medicine with him wherever he goes. A. Suffered B. Suffering C. Being suffered
时，由k递推到k+1左边应添加的因式是 
B．
D．
