The question is about the movement of sediment particles on the beach due to the action of swash and backwash, and which term correctly identifies this process. Let's break down the key terms to understand the correct answer.

Explanation of Key Terms:

1. Longshore Drift: This refers to the transportation of sand and pebbles along the coast by wave action. Waves approach the beach at an angle, carrying materials up the beach (swash), and then the backwash carries them down the beach, also at an angle. This zig-zag movement of particles along the shoreline results in longshore drift.
2. Beach Drift: This is the specific movement of sediments in a saw-tooth pattern along the beach due to the swash and backwash. Particles are moved up the shore by the swash (water rushing up the beach) and down the shore by backwash (water receding). This leads to a zig-zag movement of particles specifically on the beach.
3. Surf Zone Transport: This term generally implies the movement of sediments within the surf zone, the area between the breaking waves and the shore, but does not specifically address the swash and backwash process.
4. Breaker Zone Transport: This refers to the movement of water and sediments in the breaker zone, where waves break before reaching the shore, and similarly does not specifically describe the saw-tooth movement on the beach itself.

Conclusion:

The question specifies the "saw-tooth movement" along the beach due to alternating swash and backwash. This description matches precisely with "Beach Drift," which is defined as this exact phenomenon. Therefore, the correct answer is Beach Drift.