Which is the equation of an ellipse with directrices at y = ±2 and foci at (0, 1) and (0, −1)? x squared over 4 plus y squared over 1 equals 1 x squared over 1 plus y squared over 2 equals 1 x squared over 1 minus y squared over 4 equals 1 x squared over 1 minus y squared over 2 equals 1