Find the center, vertices, and foci of the ellipse with equation 3x2 + 7y2 = 21. a. Center: (0, 0); Vertices: the point negative square root of seven comma zero and the point square root of seven comma zero; Foci: (-2, 0), (2, 0)

b. Center: (0, 0); Vertices: (-7, 0), (7, 0); Foci: Ordered pair negative 2 square root 10 comma 0 and ordered pair 2 square root 10 comma 0

c. Center: (0, 0); Vertices: the point zero comma negative square root of seven and the point zero comma square root of seven.; Foci: (0, -2), (0, 2)

d. Center: (0, 0); Vertices: (0, -7), (0, 7); Foci: Ordered pair 0 comma negative 2 square root 10 and ordered pair 0 comma 2 square root 10