Correct Option: C  [ second incisor ]
Remark:
Explanation: The tusks of elephants are actually modified second upper incisors. They are made primarily of dentine, commonly known as ivory, and covered by a thin layer of enamel at the tip (which wears off with time). Tusks grow continuously throughout the elephant’s life and are used for digging, lifting objects, stripping bark, defense, and dominance displays.
Note: Both male and female African elephants have tusks, whereas in Asian elephants, tusks are generally present only in males.
Composition: Tusks are composed of dentine (ivory) with fine concentric growth lines, and they grow from sockets in the skull.