The answer is C. First, draw a picture. Then here's my reasoning:
1.
Insufficient We know point A has coordinates (-3, 4) and the question states point E is on the y-axis 4 points from the origin, therefore it has the points (0, Y), where Y can be equal to 4 or -4. This would give us two different distances from point A. At (0, -4) and at (0, 4) line segment AE would be two different lengths.
2.
Inufficient The question says 2AE = EC, or twice the distance between AE would equal the distance between points E and C. Now it might be helpful to plot both points C and A on a graph to get a visual idea of the problem. One thing not to do here is think you have two sides of a 30-60-90 right triangle, x and 2x because you have no idea where point E is located, expect the distance between A and E is exactly half the distance between E and C.
Now try and combine the statements. Plot each point on the graph. You'll see E must be (0, 4) for this problem to work. And plug in the numbers to the formula in 2.
2 AE = (4 - (-2)) or 2AE = 6, and the distance between points A and E (-3, 4) and (0, 4) = 3, then multiply that by 2 and you get 6.