Answer:
d. All the above choices are correct.
Explanation:
When a spring of spring constant k is compressed by distance x , the potential energy stored in it is equal to 
E = 1/2 k x²
If spring constant is 2 k , potential energy stored 
E = 1/2 2k x²
= k x²
which is twice the earlier potential energy. 
In the first case , the energy of spring is imparted to box . The energy given to box is spent by frictional force due to which box comes to rest. 
So energy of box acquired from spring = work done by frictional force. 
So energy of box acquired from spring =  F X d  , F is frictional force , d is displacement . 
In the second case , 
energy acquired by box becomes  two times 
Work done by frictional force will also become two times to put box at rest 
So displacement will be two times ( because frictional force is constant ) 
so option a is correct . 
option b is also correct .
Because kinetic energy  of box will be twice as explained above . 
So option d will be correct.