Which one of the following constitutes a business?

a$.$

A doctor coaches her old uni soccer team, she also does offers private lessons charging $$50$ a session; barely making a profit

b$.$

An office secretary collects vintage records in her spare time, buying and selling them through the internet, making a regular $$10,000-16,000$ profit each year

c$.$

A lawyer in Sydney has $37$ sheep on his weekend property in the Southern Highlands. Each year he sells the wool at a small loss.

d$.$

A dentist restores antiques in his spare time out of enjoyment and occasionally sells a piece and makes an annual profit of $$500$