In 1800, nearly 25 years after his discovering of methane gas, Alessandro Volta, the Italian physicist, had developed what would become known as the voltaic pile, the first electric battery.

A Discovery of methane gas or discovering methane gas, misplaced Alessandro Volta (he is not gas), time is specified so simple past should be used, electric battery should be placed immediately after developed followed by modifier..hence INCORRECT
B time is specified so simple past should be used, misplaced Alessandro Volta (he is not gas), incorrect tense....hence INCORRECT
C CORRECT
D discovered methane gas, Italian physicist Alessandro Volta's discovery of the first electric battery, later known as the voltaic pile....Fragment, .hence INCORRECT
E misplaced Alessandro Volta (he is not gas), seems there was another person also, incorrect tense....hence INCORRECT

