Final answer:
The real estate broker can show his thanks by paying a referral fee to Mr. White.
Step-by-step explanation:
The correct answer is d. Pay a referral fee. When Mr. White referred his sister to a real estate broker and she purchased a $200,000 home, it is common practice for the broker to show gratitude by paying a referral fee to Mr. White. A referral fee is a commission or compensation provided to an individual who refers a client or customer to a business. It is a way for the broker to thank Mr. White for the referral and acknowledge his role in bringing in new business.