Answer: D) the contrast between what is expected and what does happen.
Explanation: an irony is a state of affairs or an event that seems contrary to what one expects and it often has an amusing result. A situational irony is when what happens is the contrary to what the characters or the audience are expecting to happen. So, from the given options, the one that best represents the definition of situational irony, is the corresponding to option D: the contrast between what is expected and what does happen.