Answer: 4a.
- A a
- B 2a
- C 4a
- D a<sup>2</sup>
Correct answer: C. 4a
Explanation: The latus rectum of y<sup>2</sup> = 4ax has length 4a, the focal chord perpendicular to the axis.
All four conics form a single family distinguished only by eccentricity: a circle is the most "closed" (e=0), an ellipse is an elongated closed curve, a parabola is the borderline open curve (e=1), and a hyperbola has two separate open branches (e>1).
Concept context
Study circles, parabolas, ellipses, and hyperbolas as curves formed by intersecting a plane with a double cone, with their standard equations and key properties.