Bithiol is an antiseptic agent commonly added to soaps to impart antibacterial and antifungal properties. It is used for its ability to kill or inhibit the growth of microorganisms.
- Iodine is an antiseptic, but it's not typically used in soaps.
- Furacine is also used as an antiseptic, but not commonly in soaps.
- Terpineol is used in soaps for its pleasant fragrance but is not an antiseptic.
Thus, the correct answer is Bithiol (C).