Mark Just Placed a Stop Limit Order to Sell 100

Multiple Choice

Mark just placed a stop limit order to sell 100 shares at $21 stop, $18 limit. Which one of the following statements is correct concerning this order if the current market price is $16?

A) As soon as the price rises to $18, the stock will be sold.
B) The stock will sell for at least $18 but less than $21.
C) The stock will sell for $18 a share as soon as the price hits $21.
D) The order will become a limit order to sell at $21 once the market price reaches $18.
E) The order will become a limit order to sell at $18 once the market price reaches $21.