In the context of equity trading, investors must choose appropriate order types to effectively implement their trading strategies. Consider the following scenario:

John is an institutional trader looking to execute a large order without significantly impacting the market price of the stock. He is concerned about sharp price fluctuations after placing his order and wants to ensure that he can execute the entire order before the trading session ends today.

Which order type should John use to achieve his objective? Each order type has its own advantages and risks when it comes to execution, especially in a volatile market.