Answer:
4) The broker is either a Buyer's Agent or a Transaction Broker or a Seller's Agent
Step-by-step explanation:
I guess that by common sense the buyer should know beforehand if the broker worked for him or not, but it is possible that the buyer doesn't know if the broker is a transaction broker or a seller's agent.
Anyway, it is always best to be completely sure, specially because the broker earns a commission fee and depending on who he/she works for, will be responsible for paying that fee. Also, a seller's agent should always try to get the highest possible price, while the buyer's agent should always try to get the lowest possible price.