4. Sometimes workers a. have to wear a special uniform with a tag; b. never have to wear a special uniform; c. can refuse from wearing a tag.

This is a multiple-choice question related to workplace regulations. Without further context or a specific scenario, it's impossible to definitively determine the correct answer. However, generally, if a workplace mandates a special uniform for safety, identification, or professionalism, employees are typically required to wear it as a condition of employment. Refusal might lead to disciplinary action. The necessity of a uniform often depends on the nature of the work and company policy.

To provide a specific answer, more information about the context of these 'workers' and their 'special uniform' would be needed.

If this were a general knowledge question about typical workplace rules where uniforms are mandated:

a. have to wear a special uniform with a tag;