The part of the external ear that helps in the catching of the sound is the pinna. The ear canal and the pinna are the parts of the external ear of humans. The pinna is the part which is skin-covered and is present on the side of the head. The cartilage supports the pinna. However no cartilage is present in the ear lobe. The pinna is the visible part of the ear. The sound is transmitted to the ear canal after the sound waves are channeled through the pinna.
Hence, the correct answer is 'Option C - Pinna'.