Answer:
Broker A is responsible for safekeeping previous records up to 4 years in the past.
Explanation:
Even if broker A decided that it was best for him to start working for broker B, he/she is still responsible for safekeeping all the previous records (up to 4 years) when he worked by himself/herself. The same applies if broker B had acquired broker A's business (a sole proprietorship is a type of business).
