In each of the question ,four alternative are given for the Idiom/Phrase.Choose the alternative which best expresses the meaning of the Idiom/Phrase.
A dark horse

Options

A. A wild animal
B. A black horse
C. An unknown entry
D. A front runner

Answer

C

Explanation

A dark house=a little known person or thing that emerges to prominence,an unknwon entry.
Look at the sentence:You can never say,some dark horse may come along and win a House of Lords seat.