Explanation:

- The sentence discusses how a scheme educated officers to handle situations that could become problematic by "defusing" them.

- Defuse means to make a tense or dangerous situation less hostile or dangerous.

- Option 1: Heighten

- Means to increase or make something more intense.

- This is the opposite of defuse because rather than reducing tension, it increases it.

- Correct Answer: This option is opposite in meaning to "defuse."

- Option 2: Reduce

- Means to make something smaller in size or amount.

- Similar in meaning to defuse, as it implies lowering intensity.

- Option 3: Lessen

- Means to decrease or make less intense.

- Similar to defuse; both aim at reducing tension or danger.

- Option 4: Diminish

- Means to make or become less.

- Aligned with defuse; both are about reducing or minimizing tension.