When a pendulum swings from position A to position B (assuming position A is the highest point and B is the lowest point in its swing), the total mechanical energy is conserved if we do not consider friction or any other forms of energy loss.
The total mechanical energy (E) of the pendulum is the sum of its potential energy (PE) and kinetic energy (KE). At position A, the pendulum has maximum potential energy and zero kinetic energy, while at position B, it has maximum kinetic energy and minimum potential energy. However, the total mechanical energy remains constant throughout the swing.
Therefore, the correct answer is:
It remains the same.