What Is the Bid-Ask Spread

What is the bid-ask spread?

A) the difference between the lowest price being quoted to sell a stock and the highest price being quoted to buy that stock
B) all of the costs and fees that a stock exchange charges in order to process a transaction
C) the rise or fall in the value of a stock between the time it is acquired by an investor and sold by that investor
D) the difference in the selling price of a stock between different exchanges
E) the change in the price of a stock from the market's open to the market's close