Answer:
B.commercial source
Step-by-step explanation:
Given that a Commercial source of information is a form of secondary source of information in which the information is not free but paid for.
Hence, in this case, when Mr. Isaac consults a broker (who will eventually be paid for his services) as to which houses are available for purchasing, He is consulting a "COMMERCIAL SOURCE).
It is not a personal source because a broker is not a friend or family member.
It s not a public source because a broker is not a government official nor his services are free.
It is not an experimental source of information because it does not involve trying products