Let a and b be non-zero real numbers. Then, the equation
$$(ax^2 + by^2 + c)(x^2 - 5xy + 6y^2) = 0$$
represents

A

four straight lines, when c = 0 and a, b are of the same sign

B

two straight lines and a circle, when a = b, and c is of sign opposite to that of a

C

two straight lines and a hyperbola, when a and b are of the same sign and c is of sign opposite to that of a

D

a circle and an ellipse, when a and b are of the same sign and is of sign opposite to that of a