After a long day of hiking, my car unexpectedly _________________, leaving me stranded on the side of the road.

Explanation

The most appropriate phrase for the blank in this statement is: “broke down”. In the context of a car, "broke down" means to stop working suddenly or to suffer a mechanical failure. It fits well with the situation described in the sentence. So, the completed statement would be: "After a long day of hiking, my car unexpectedly broke down, leaving me stranded on the side of the road." Explanation of incorrect options: Back down (option a): This phrase means to withdraw or concede in a conflict. It doesn't fit the context of a car malfunction. Call around (option b): This phrase means to contact various places or people for information. It doesn't convey the idea of a car breaking down. Back up (option c): This phrase generally means to provide support or assistance. It doesn't fit the context of a car experiencing a mechanical failure. Blow up (option d): This phrase usually refers to an explosion, and it doesn't accurately describe a car malfunctioning in the given context.