The correct answer is A. Margin trading.
Margin trading is a type of investment strategy in which an investor borrows money from a broker to purchase securities. The investor then uses the securities as collateral for the loan. Margin trading can be a risky strategy, as it can lead to large losses if the value of the securities declines. However, it can also be a profitable strategy, as it allows investors to purchase more securities than they would be able to afford with their own money.
B. Curb dealing is a type of over-the-counter trading that takes place in an informal market. Curb dealing is often used to trade securities that are not listed on a formal exchange.
C. Badla is a type of stock lending and borrowing system that is used in India. Badla allows investors to borrow shares from other investors in order to sell them short.
D. Forward is a type of contract that allows two parties to agree to buy or sell an asset at a specified price on a specified date in the future.