A:蛋白质的变性
B:蛋白质的盐析
C:氯化铁的水解
D:醋酸的电离
若(x2+y2)(x2+y2﹣1)=12,则x2+y2=____.
关于CO和CO2的说法错误的是
Helen is going to work in an old people's home to help ________ the old people.
竖直竹杆长9m,它的下端离1m高的窗口上沿1.25m,放手让竹杆自由下落,它通过窗口所需的时间为:(g取10m/s2)( )