A:①②③三个过程中已经发生了基因突变的是②③
B:①②过程不仅发生染色体变异还可能发生基因重组
C:②过程中细胞的遗传物质改变,导致细胞发生脱分化
D:V细胞与已免疫的小鼠B细胞融合能用于制备单克隆抗体
现代历史上,科技、艺术领域人才辈出。属于绘画领域的代表人物是( )
某同学利用打点计时器和气垫导轨做“探究碰撞中的不变量”的实验,气垫导轨装置如图1甲表示,所用的气垫导轨装置由导轨、滑块、弹射架等组成.在空腔导轨的两个工作面上均匀分布着一定数量的小孔,向导轨空腔内不断通入压缩空气,压缩空气会从小孔中喷出,使滑块稳定地漂浮在导轨上,如图1乙所示,这样就大大减小因滑块和导轨之间的摩擦而引起的误差.
【旅游地理】阅读材料,回答问题。
庐山位于江西省北部,庐山风光以“奇,秀,险,雄”闻名于世,素有“匡庐奇秀甲天下”的美誉。庐山先后被评为首批国家级风景名胜区、首批5A级旅游区、首批世界地质公园,并入选“世界遗产名录”。四季景色各异,具有“春如梦、夏如滴、秋如醉、冬如玉一的特点,下图是庐山多年平均各月旅游人口分布示意图。
据上图分析说明庐山多年平均各月旅游人口分布特征及其原因。
刘俊问王老师的年龄时,王老师说:“我像你这么大时,你才3岁;等你到了我这么大时,我就45岁了.”设王老师今年x岁,刘俊今年y岁,根据题意,列方程组正确的是( )
“ Dreams may be more important than sleep. We all need to dream.” some scientists say. Dreams take up about one quarter of our sleeping time. People have several dreams each night. Dreams are like short films. They are usually in color. Some dreams are like old films. They come up over and over again. That may be the dreamer worrying about something. Dreaming may be a way of trying to find an answer. Some people get new ideas about their work from dreams. They may have been thinking about their work all day. These thoughts can carry over into dreams. Too much dreaming can be harmful. The more we sleep,the longer we dream. The mind is still at work when we dream. That is why we may have a long sleep and still wake up tired.