Answer: 0.
- A 0
- B 1
- C Between 0 and 1
- D Greater than 1
Correct answer: A. 0
Explanation: A circle is a special conic with eccentricity e = 0, since it has no distinct directrix and constant radius.
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.