Which of the following is the condition for a second order partial differential equation to be hyperbolic?

Which of the following is the condition for a second order partial dif

1.	Which of the following is the condition for a second order partial differential equation to be hyperbolic?
A.	b<sup>2</sup>-ac < 0
B.	b<sup>2</sup>-ac=0
C.	b<sup>2</sup>-ac>0
D.	b<sup>2</sup>-ac= < 0
Answer» D. b<sup>2</sup>-ac= < 0