Please help select the best answer

[funsosweet]

In the match against the Uplanders team,the submariners turned out to be the dark horse

a. played most brilliantly

b. played below their usual form

c. won unexpectedly

d.lost as expected

e. won as expected


I have an exam so I need clarification

[Tdol]

Dark horse: http://www.usingenglish.com/referenc...ark+horse.html
A dark horse in a sporting even would almost certainly be c) in my opinion.