Final answer:
The correct answer is b) Vary the start times and route; this introduces randomness and unpredictability to the patrols without compromising coverage effectiveness.
Step-by-step explanation:
To reduce the predictability of your patrols, the best approach would be b) Vary the start times and route. By doing this, you can ensure that the pattern of your patrols remains random to anyone who might be observing them. Reducing the frequency could potentially compromise the effectiveness of the patrols by leaving gaps in coverage. Instead, varying the times and the routes taken keeps the patrol schedule dynamic and unpredictable, making it difficult for unwanted observers to predict when you will be patrolling a certain area.