The total mechanical energy of a system: a) can never be negative. b) is constant, if only conservative forces act. c) is either all kinetic energy or all potential energy, at any one instant. d) is not uniquely determined for most naturally occurring systems. e) is equally divided between kinetic energy and potential energy.

Option B).

Explanation:

This cab be explained as:

The total mechanical energy of a system can be negative. Since, the total mechanical energy is the sum of kinetic and potential energy of a system and kinetic energy can never be negative but the potential energy can be depending upon the magnitude and field of force. if attractive field of force is present and the magnitude of kinetic energy is less than that  of potential energy then the total energy will be zero.  The total mechanical energy of a system is constant under the action of conservative fields as in non- conservative fields, the forces acting will result in loss of energy from the system which is prevented in  conservative field.There can't be either only kinetic energy or only potential energy.The  total mechanical energy of a system can be uniquely determined for most naturally occurring systems.The  total mechanical energy of a system is not equally divided between kinetic and potential energy  and varies accordingly.