Answer:
A. The firm's Executives
Step-by-step explanation:
External Sources to a firm are those sources that are related to be not part of the day to day running of the affairs of the firm. As such the firm's executives are internal sources because they represent the interest of the firm.
In case of a sole proprietorship or partnership business, these executives are the owners of the business while in the case of listed firms, they represent the interest of the owners of the firm. They cannot therefore be regarded as external sources
Competitors are related as they are within the same product line but they are not involved in the daily affairs of the firm, suppliers make raw materials available while customers patronise the business. Trade shows magazine on the other hand independently report the progress of all firms within the industry. These are the external sources.