A buy and selling contract的用法和样例：
- Investors can buy and sell on a daily basis.
- At the close of every trading day, the clearinghouse matches buy and sell contracts for the day.
- At the close of every trading day, the clearing house matches buy and sell contracts for the day.
- Cross When a broker receives a buy and sell order for the same stock at the same price, and subsequently makes a simultaneous trade between two separate customers.
- Money is a medium for buying and selling.