The spring extends by on loading then the energy stored by the spring is (if is the tension in spring and is spring constant)
Step 1: Given parameter
The spring extends by x on loading
Step 2: Parameter to be calculated
Energy stored by the spring
Step 3: Calculating the energy stored
The relation between the spring constant and tension is
This implies that
Also, the energy stored in the spring is
Using equation (1), the expression of energy becomes
Thus energy stored by the spring is
Hence, option (A) is correct.