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

• A
  $A$ circle and an ellipse,when $a$ and $b$ are of the same sign and $c$ is of sign opposite to that of $a$.
• B
  Two straight lines and a hyperbola,when $a$ and $b$ are of the same sign and $c$ is of opposite sign to $a$.
• C
  Four straight lines,when $c = 0$ and $a, b$ are of the same sign.
• D
  Two straight lines and a circle,when $a = b$ and $c$ is of sign opposite to that of $a$.