Final answer:
A person hired by a broker-dealer with an existing brokerage account must provide written consent to their new employer within 14 days of being hired, according to FINRA rules.
Step-by-step explanation:
The subject of this question is related to the regulatory requirements for a person who is hired by a broker-dealer and already has an existing brokerage account with an online trading securities firm. According to the Financial Industry Regulatory Authority (FINRA) rules, such an individual must provide written consent regarding their account to the hiring broker-dealer. The correct answer is B) 14 days. This means that within 14 days of starting their new position, the individual must inform their new employer in writing about their existing account and obtain the firm's approval to maintain it.