Mr. Han has a son and he is happy.
A:3 year old
B:3-year-old
C:3-years old
D:3 years old
下列句子中,没有语病的一项是( )
设点P是双曲线x2a2-y2b2=1(a>0,b>0)与圆x2+y2=a2+b2在第一象限的交点,F1,F2分别是双曲线的左、右焦点,且|PF1|=2|PF2|,则双曲线的离心率为( )