A customer enters an order to buy 100 shares of JKL at 50 stop-limit when the market price is 49.75. The ticker tape after the order shows the following transactions:

49.80, 49.75, 50, 50.13, 50.25, 50.13, 49.88

The first trade where the order could have been executed is

A. 50.13

B. 49.88

C. The order could not have been executed

D. 50