Explanation:

- Parthenium hysterophorus is commonly known as Carrot grass.

- Option 1: Lemon grass - This is incorrect. Lemon grass is a completely different plant used extensively in cooking and has a distinct citrus flavor.

- Option 2: Lawn grass - This is a general term for grasses used in lawns and not specific to Parthenium hysterophorus.

- Option 3: Horse grass - This option is not commonly associated with Parthenium hysterophorus.

Carrot grass is a weed known for its rapid spread and adverse effects on agriculture and human health.