The Otto cycle is typically depicted on a P-V diagram through a series of processes that are characteristic of internal combustion engines. Let's break down the path followed by the Otto cycle:

1. Compression (1-2): The air-fuel mixture is compressed adiabatically as the volume decreases and pressure increases.
2. Combustion (2-4): The mixture is ignited, typically represented by a vertical line indicating constant-volume heat addition, leading to an increase in pressure.
3. Expansion (4-7): The high-pressure gases expand adiabatically, pushing the piston and increasing volume while pressure decreases.
4. Exhaust and Intake (7-1): The burnt gases are expelled, and a new charge is taken in, which completes the cycle back to the original state at point 1.

In the given P-V diagram, the path 1-2-4-7-1 effectively represents these processes:

• 1 to 2: Adiabatic compression.
• 2 to 4: Constant-volume heat addition (combustion).
• 4 to 7: Adiabatic expansion.
• 7 to 1: The return to the starting state, completing the cycle.

Thus, the correct path representing the Otto cycle in the provided diagram is 1-2-4-7-1. Therefore, the correct answer is: