The table shows the recipe and the available ingredients for making the maximum possible number of sandwiches.

Making Sandwiches
Recipe for One Sandwich Total Ingredients Available
2 tomato slices, 4 cucumber slices, 2 bread slices 8 tomato slices, 22 cucumber slices, 8 bread slices

If the ingredients represent reactants of a chemical reaction, which of the following represents the leftover reactant?