The police officer was sacked because he gave … the command's secret.

Analyze the question: The sentence needs a phrasal verb that means to reveal or disclose something secret. The police officer was sacked because he did this with the command's secret.

Explain the concept: The verb "give" forms different phrasal verbs depending on the particle that follows it:

• give off means to emit (smell, heat, light). Example: "The gas gives off a bad smell."
• give in means to surrender or yield. Example: "He gave in to pressure." It does not take a direct object like "secret."
• give away means to reveal or disclose, or to hand something over for free. Example: "He gave away the secret."
• give up means to quit or surrender. Example: "She gave up smoking."

Step-by-step solution:

1. The sentence says he was sacked for what he did with a secret.
2. The action must be revealing or leaking the secret.
3. "Give off" would mean emit, which makes no sense for a secret.
4. "Give in" means surrender, and it does not fit with an object.
5. "Give up the secret" could loosely mean to surrender or divulge it under pressure. However, the standard idiom for betraying or leaking a secret is "give away", and it fits best here.

Answer: The correct option is C. away.

Tip: Remember the collocation "give away a secret" (also "give the game away"). When a question is about disclosing information, think "give away." "Give up" usually goes with quitting a habit or surrendering.