—When is ________ birthday?
—________ birthday is on April 20th.
A:John's; He
B:John; Him
C:John's; His
D:John; He's
抛物线y=x2-4x-7的顶点坐标是( )
如图是果树的一段枝条,长有大小相同的两个果实.已对枝条的两个部位的树皮进行了环剥.以下叙述错误的是( )