Explanation:

- Abetment in the Indian Penal Code refers to the act of instigating, engaging, or aiding someone to carry out a crime.

- A person of unsound mind cannot be a principal offender due to mental incapacity but can technically be abetted in a crime since the abettor's intent plays a crucial role.

- An infant generally lacks the intent to commit a crime due to age and understanding, yet abetment provision still applies if another party incites the criminal act.

- Option 1 and Option 2 include those who legally aren't capable of committing crimes alone, but can still be abetted.

? Option 3: Both (a) and (b) is the correct answer.