The physical quantity whose S.I unit is the same as that of the force constant is:
A. pressure
B. surface tension
C. potential energy
D. torque

Hint :In order to the question, as we know the relation between the force constant and the optional physical quantities, we should go through the definition of all the given physical quantities.

Complete Step By Step Answer:
The physical quantity whose S.I unit is the same as that of the force constant is surface tension. As both S.I units are the same as Newton per metre.
Surface tension is the property of any liquid by virtue of which tries to minimize its free surface area.
Surface strain of a fluid is estimated as the power acting per length on a fanciful line drawn digressively on the free surface of the fluid.
Surface tension, $ \;S = Force/Length = {\text{ }}F/l{\text{ }} = {\text{ }}Work{\text{ }}done/Change{\text{ }}in{\text{ }}area $
It is a scalar quantity. Surface tension is a molecular phenomenon which is due to cohesive force and the root cause of the force is electrical in nature. Surface tension of a liquid depends only on the nature of liquid and independent of the surface area of film or length of the line. Small liquid drops are spherical due to the property of surface tension.
Whereas, in physical science, a force constant is another term for a spring constant, as characterized by Hooke's law. It is a proportionality steady, more definitely. The strength steady k is identified with a situation's unbending nature (or firmness), the more noteworthy the consistent power, the more prominent the reestablished power, and the stiffer the framework.
Hence, the correct option is B. surface tension.

Note :
Spring constant or also known as the force constant is the restoring force per unit extension in the spring. Its value is determined by the elastic properties of the spring. The spring followed a linear response against applied force, demonstrating the validity of Hooke's law at the nanoscale.