Explanation:

- Machhi Singh vs State of Punjab (1983): This case is significant in India's legal history as it laid down the principles on which the death sentence can be awarded, elaborating on the "rarest of rare" doctrine established in the Bachan Singh case.

- Bachan Singh vs State of Punjab (1980): This landmark case challenged the constitutionality of the death penalty in India. The Supreme Court upheld its validity but introduced the "rarest of rare" doctrine, which significantly restricted the imposition of capital punishment.

- DP Bhullar Case (2013): Devinder Pal Singh Bhullar was sentenced to death for his involvement in a terror attack. The plea of mental illness was a significant aspect of this case, raising debates over the humane considerations in capital punishment cases.

- Bhagwan Das Case (2011): This case reinforced the "rarest of rare" doctrine. Bhagwan Das was sentenced to death for committing honor killing, highlighting the gravity of such crimes in India.

Correct Answer: Option 4 (1, 2, 3 and 4): All listed cases are related to the issue of capital punishment in India.