Final answer:
The word 'Unwitting' goes with the phrase 'didn't see it coming,' as it describes an action done without awareness, encapsulating the surprise element of the phrase.
Step-by-step explanation:
The phrase “didn’t see it coming” is often used to express that someone was taken by surprise or was unaware that something was going to happen. Out of the options provided, the word “Unwitting” goes with “didn’t see it coming.” Unwitting is an adjective that describes something done without awareness or intention. It captures the essence of being unaware, hence not anticipating the event, just as the phrase suggests. Correspondence, on the other hand, is unrelated to the context of surprise or lack of anticipation and typically means communication, usually in the form of letters or emails.