• Reproductive Physiology of the Guinea Pig (Cavia porcellus):
• The normal gestation period of the guinea pig is 59 to 72 days (averaging approximately $68\text{ days}$).
• Because of this exceptionally prolonged gestation among small rodents, guinea pig pups are born precocial—fully furred, eyes and ears open, and able to consume solid pelleted feed within hours of birth.
• Gestation Periods of Other Laboratory Animals:
• Mouse: $19\text{--}21\text{ days}$
• Rat: $21\text{--}23\text{ days}$
• Hamster: $16\text{ days}$
• Rabbit: $30\text{--}33\text{ days}$

Correct option: (3) 59-72 days