Final answer:
The frequency of site visits depends on the specific requirements of the project and could vary, suggesting 'As necessary' might be the correct choice. However, without additional context, a definitive answer cannot be provided.
Step-by-step explanation:
This question seems related to a professional or technical scenario rather than an academic subject, particularly since it refers to a schedule for visiting a site. This could apply to fields like construction, engineering, or project management. In such contexts, the frequency of site visits depends on many factors including the project phase, the criticality of the work being performed, and the specific requirements as outlined by the project management plan or client specifications.
The answer could be (c) As necessary, as the requirement for site visits typically depends on the specific circumstances of the project and might not adhere to a strict schedule like weekly or monthly. However, without more context about the nature of 'the site' or the kind of oversight or work involved, it's not possible to give a definitive answer.