In Which of the Following Situations Would a Business Letter

In which of the following situations would a business letter probably be the most effective communication channel?

A) The area manager of a large home furnishings chain needs to let 14 store managers know about a new procedure for handling large shipments.
B) The administrative assistant of a charitable organization has been asked to solicit donations in the form of goods and services from retailers to sell at a charity auction.
C) One employee of an organization needs information from a co-worker in order to complete a financial report.
D) The human resources manager of a national marketing group needs to inform all employees about how to access a year-end T4 online.