C

Step 1: Evaluate Statement I: The work done by a force is calculated using the formula Work = Force x Distance x cos(θ), where θ is the angle between the force and the direction of movement. In a round trip, the initial and final positions of the body are the same; thus, the net displacement is zero. Therefore, the net work done on the object as it returns to its starting point is zero, which supports the assertion that the work done by or against friction in a round trip is zero.

Step 2: Evaluate Statement II: Friction is not a conservative force; it is a non-conservative force. A non-conservative force, such as friction, dissipates energy as heat and does not store potential energy like conservative forces (e.g., gravity). Therefore, if work is done against friction, energy is lost, and a path-dependent force exists rather than one where the work done is independent of the path taken.

Conclusion: Since Statement I is true (the work done in a round trip is zero because the displacement is zero), but Statement II is false (friction is not a conservative force), the correct choice is Option C.