Answer: The spring that is oscilating faster (has bigger frequency)
Step-by-step explanation:
We know that the frequency of oscilation of a spring is:
w = √(k/m)
Where k is the spring constant and m is the mass of the blocks, then if both blocks are identical, also their mases.
This means that if we see that one of the springs oscilates faster ( the frequency is larger) this should mean that the spring constant is larger.