Option 1: Meerut - This option is incorrect. The correct answer is not Meerut because the first shot from a rebel`s gun in 1857 was not fired in Meerut.

Option 2: Ambala - This option is incorrect. The correct answer is not Ambala because the first shot from a rebel`s gun in 1857 was not fired in Ambala.

Option 3: Barrackpore - This option is correct. In 1857, the first shot from a rebel`s gun was fired in Barrackpore. This event is considered one of the significant incidents that sparked the Indian Rebellion of 1857.

Option 4: Delhi - This option is incorrect. The correct answer is not Delhi because the first shot from a rebel`s gun in 1857 was not fired in Delhi.

In summary, the correct answer is option 3: Barrackpore. This location marks the beginning of the Indian Rebellion of 1857 when the first shot was fired from a rebel`s gun.