S03 Q22 :S
Think of it this way: if it were just 1 spring at the beginning, the extension is 3x, since they are 3, the extension is x
1 is removed, so now its 3x / 2 , which is 1.5x
The load is doubled, so 2 * 1.5x
Which is 3x, response D.
Hope that was clear, i understood it that way