Choose the appropriate meaning of the given Idiom/Phrase Dark horse

Solution

The idiom "dark horse" means one who wins or succeeds unexpectedly, typically a candidate or competitor about whom little is known.

• Why this fits: A dark horse is someone who surprises others by performing much better than anticipated.

• Why the other choices are wrong: "A black horse" is a literal reading, "a difficult problem" is not an idiomatic meaning, and "subject of a dispute" describes a different concept.

Example: The underdog team was considered a dark horse in the competition and went on to win the championship.

Therefore, the correct meaning of the idiom is one who wins unexpectedly.