Final answer:
Managers should encourage staff to support a no-smoking policy, as it fosters a positive and compliant work atmosphere. 'Encourage' is the most appropriate term as it suggests a supportive and motivational approach by managers.
Step-by-step explanation:
Managers should encourage staff to maintain the no-smoking policy throughout the building. The use of 'encourage' here indicates that managers are to support and motivate their staff to comply with the policy in a positive manner. While instructing, training, and disciplining are also actions managers might take in different contexts, encouragement aligns with creating an environment where staff voluntarily adhere to company policies due to a sense of shared responsibility and understanding of the importance of a smoke-free environment.