括号内是区别下列各组常见物质的试剂方法，其中错误的是A．硬水与软水（肥皂水，振荡） B．水与双氧水（加入少量二氧化锰粉末
The letter was returned because the person _________ it was addressed had died three years ago. A. to whom B. to which C. which D. wh
14．(2013·保定市重点高中调研考试)下面是弗来明对青霉素的早期研究过程：发现问题——在培养细菌的器具中发现一种青霉菌，在这种青霉菌的周围没
下列叙述不合理的是（ ） A. 倡导“低碳”生活，多步行，少开车 B. 为减少“白色污染”，自带购物布袋 C. 用水扑灭因电线老化短路而引起的火灾 D.
Have you ever wished to have an umbrella that makes your hands free? Alan Kaufman has come up with the Nubrella, which means new + umbrella. It is the first truly hands-free umbrella in the world.
下列各组内的物质，按单质、化合物、混合物的顺序排列正确是（ ） A．固态氮、矿泉水、水泥砂浆B．液态氮、蒸馏水、过氧化氢溶液C．稀有气体、
Read the following advertisements and then choose the correct answers. (China Daily, March 3, 1996) the biggestshopping center will open on March 8. Every body with today's China Dailywill get a smal
下列关于蛋白质生物合成的叙述,正确的是 A.一种tRNA可以携带多种氨基酸 B.DNA聚合酶是在细胞核中合成的 C.反密码子位于tRNA上 D.线粒体中的DNA不能进行
