一列简谐横波沿x轴负方向传播，波速v=4 m/s，已知坐标原点（x=0）处质点的振动图象如图a所示，在下列4幅图中能够正确表示t=0.15s时波形的图是
On March 14, violent crimes of beating, looting and burning in Lhasa of Tibet broke out, _____ 13 innocent people and with more than 300 _____. A. killed; injured B. killing; injured C. ki
Are you sometimes a little tired and sleepy in the early afternoon? Many people feel this way after lunch. They may think that eating lunch is the cause of the sleepiness. Or, in summer, they m
从接近原料产地考虑，法国应将葡萄酒厂建在（ ） A.地中海沿岸 B.比斯开湾沿岸 C.塞纳河沿岸 D.加龙河沿岸
把2.3 g钠投入到97.7 g水中，反应完毕后所得溶液中溶质的质量分数是（ ）A.2.3% B.4.0% C.大于4.0%
下列物质中，不属于氧化物的是 A.CO B.Na2O C.MnO2 D.KClO3
世博会中国馆、主题馆等建筑所使用的光伏电池，总功率达4兆瓦，是历届世博会之最。下列有关叙述正确的是( ) A．光伏电池是将太阳能转变为电能 B
把锌片和铁片放在盛有稀食盐水和酚酞试液混合溶液的玻璃皿中，经过一段时间后，首先观察到溶液变红的区域是( ) A．Ⅰ和Ⅲ附近 B．Ⅰ和Ⅳ附近 C
