Parthenium- Threat to biodiversity
Parthenium or carrot grass is an alien species. When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn invasive and cause decline or extinction of indigenous species. Such species are also called exotic or introduced species. Thus, Parthenium is a threat to biodiversity as it competes with our local species for the limited resources. So, the correct answer is 'Parthenium- Threat to biodiversity'.