(A) Onslaught - a fierce or destructive attack
(B) Arrogant - having or revealing an exaggerated sense of one's own importance or abilities
(C) Fortitude - courage in pain or adversity.
(D) Nepotism - the practice among those with power or influence of favoring relatives or friends, especially by giving them jobs
The given word Bravery means courageous behavior or character. From the given options we can see that option (C) is the perfect fit. Hence the answer is option (C).
Note that option (A) is not a description of a person or his/her qualities. Option (B) and Option (D) are completely different qualities of humans.