Concept:A jobber is a principal in the stock exchange who trades securities using his own funds and for his own account.
Explanation:The question asks for the member who buys and sells securities on his own, meaning he acts as a principal, not as an agent.
A jobber deals only with brokers, not directly with the public, and holds securities on his own books.
By buying and selling on his own account, a jobber provides market liquidity and helps match buy and sell orders.
A broker acts as an agent for clients, a promoter helps launch new companies, and a speculator takes risks to profit from price movements.
Therefore, the correct member is the jobber.
Answer:A. jobber