My father was reading a book ________ I was doing my homework.
A:before
B:after
C:when
D:while
胰岛素是胰岛素原通过蛋白酶的水解作用而生成的,那么胰岛素原水解所需的水中的氢用于( )
数列{an}中,a1=1,an+1=2an+1,则通项an=____
已知两圆的半径R、r分别为方程x2-5x+6=0的两根,两圆的圆心距为1,两圆的位置关系是( )
若a<0,则( )