Passage Summary: The police chief forbids drinking on the job but makes an exception for undercover cops in nightclubs because their work is considered very important.

Conclusion: Undercover officers investigating crime-heavy nightclubs are permitted to consume alcohol in moderation despite the general ban on drinking while on duty.

Reasoning: The police chief believes that undercover work in these specific environments is highly valuable to the department's mission.

Analysis: To strengthen this argument, we need to bridge the gap between the 'value' of the work and the necessity of the exception. The chief assumes that drinking is actually required to perform this valuable work effectively. Look for an answer choice that suggests an officer's cover would be blown or their investigation hindered if they refused to drink in a nightclub setting. If the exception is necessary for the success of the 'valuable' mission, the chief's policy becomes much more justifiable.