A:双亲表现型正常,生出一个患病女儿,必为常染色体隐性遗传
B:母亲患病,父亲正常,子代中有正常儿子,不是X染色体隐性遗传
C:双亲表现正常,生出一个色盲女儿的几率为零
D:一个具有n对等位基因的杂合子,必定产生2n种配子
自然灾害的频发足以毁灭我们的地球,灾害中常有如下现象发生,其中属于化学变化的是( )
—Did you have a good time?
—It couldn't be worse. We were held up on the expressway for three hours. On the way back, we found the car got a f____ tyre, and the spare was, too.
钝角三角形ABC中,∠BAC>90°,∠ACB=α,∠ABC=β,过点A的直线l交BC边于点D.点E在直线l上,且BC=BE.