When Does the Equation X² + Y² + Z²

Multiple Choice

When does the equation x² + y² + z² + Ax + By + Cz + D = 0 represent a sphere?

A) if and only if A² + B² + C² + D > 0
B) if and only if A² + B² - C² > D
C) if and only if A² - B² + C² > 0
D) if and only if A² + B² + C² > 4D
E) if and only if A = 0, B = 0, C = 0, and D < 0