The Earth has warmed by about half a degree（0．50℃）over the last 100 years．It could be getting warmer on its own，but many scientists think that people are making the Earth warmer by making
-------I bet someone stole my backpack . -------Well , you ______ have kept an eye on it . A.mayB.canC.wouldD.should
如图所示的实验装置中所反映的物理原理对发电机有直接影响的是
如图所示，一根均质绳质量为M，其两端固定在天花板上的A、B两点，在绳的中点悬挂一重物，质量为m，悬挂重物的绳PQ质量不计。设α、β分别为绳子端
某化学活动小组欲用右图所示装置进行实验制取漂白液(次氯酸钠和氯化钠的混合溶液)，并提高次氯酸钠含量。图中瓶乙盛饱和食盐水，瓶丙盛浓硫酸，
非凡的蜻蜓（10分）在昆虫中，蜻蜓的飞行别具一格。不仅飞快的速度令人惊叹，还有那悠闲、自如的飞行姿态也常是变幻莫测，尤其是在变换方向时，
我国饮用矿泉水的基本类别是碳酸水、硅酸水和锶水。此外还有锌、锂、溴、碘及硒矿泉水等，这里的锌、锂、溴、碘、硒是指（ ） A．原子 B
_____ he’s only been learning English for a year, he speaks it very well. A. Considered B. Considering C. Having considered D. To consider
