Answer :
B. The other sentences either have singular subjects with plural verbs (the sun... were shining; don't a combination... make) or plural subjects with singular verbs (shoes... was).
I would also have to say B is the correct answer. Your verb is was and it agrees with chance, which in this case is your noun because at success would be a prepositional phrase. Small is an adjective that describes chance.
Hopefully this helps and good luck!! :)