Answer: C
Correct answer: capable of leading
Capable takes of followed by a gerund: capable of leading. It is never followed by an infinitive. The adjective it is confused with is able, which does take the infinitive: able to lead. Both sentences would be correct if the adjective were changed to match the construction, and it is the mismatch that is at fault rather than either word by itself. A group of adjectives takes of with a gerund in the same way, and the set is worth learning: afraid of failing, fond of reading, proud of winning, tired of waiting, ashamed of lying, confident of succeeding, desirous of joining and guilty of cheating. The rule beneath all of them is that a preposition is always followed by a gerund, never by an infinitive - which is why capable to leading fails too, treating the infinitive marker to as though it were a preposition.