Explanation:

- Preventive Detention: This refers to the act of detaining an individual without trial, to prevent them from committing future offenses. It's generally used as a security measure.

- Discrimination Law: These laws are designed to prevent unfair treatment of individuals based on characteristics like race, religion, or gender. This is not related to General Dyer's command.

- Simon Law: This is a misleading term, as it doesn’t refer to an actual law. The Simon Commission of 1927 in India was a group of British lawmakers whose task was to study constitutional reform.

- Martial Law: Imposed by General Dyer, this law involves military control over normal civil functions, often during emergencies. It was enforced in Punjab during the unrest after the Jallianwala Bagh massacre.

Your interpretation aligns with historical events.