Q.Which of the following is not an invasive alien species in the Indian context?

The question asks you to identify which of the four plants is not an invasive alien species in India. Invasive alien species are those introduced from outside their natural range that spread aggressively, often harming native ecosystems.

From the NCERT textbook (Class 12 Biology, Chapter 13), three of these are explicitly named as invasive alien species that have caused major damage to India's native biodiversity:

• Lantana (Lantana camara) is a well-known invasive shrub.
• Parthenium (Parthenium hysterophorus), also called carrot grass or congress grass, is a notorious invasive weed.
• Eichhornia (Eichhornia crassipes), commonly known as water hyacinth, is an aquatic invasive that chokes water bodies.

The odd one out is Cynodon (Cynodon dactylon), which is the common lawn grass "doob" or Bermuda grass. It is a native species to the Indian subcontinent, not an introduced invasive. While it can be aggressive in gardens, it is not classified as an invasive alien species in the Indian context.

The question asks you to identify which plant is not an invasive alien species in India. To answer this, you need to recall what the NCERT textbook says about invasive alien species and then check each option against that list.

Invasive alien species are organisms introduced — deliberately or accidentally — into a region where they are not native. Once there, they spread aggressively, outcompete local species, and often cause ecological or economic harm. The NCERT textbook for Class 12 Biology (Chapter 13, Biodiversity and Conservation) gives a clear set of examples of such species in the Indian context. It mentions Lantana, Parthenium (commonly called carrot grass or congress grass), and Eichhornia (water hyacinth) as notorious invasive aliens that have invaded large areas across India. These three are textbook examples, and you will find them listed together in the same paragraph.

Now look at the fourth option: Cynodon. Cynodon is the scientific name for a genus of grasses, the most familiar species being Cynodon dactylon — known in India as doob grass or Bermuda grass. This grass is native to the Indian subcontinent and has been part of the landscape for centuries. It is not an introduced invader; it is a natural, widespread component of Indian grasslands, lawns, and roadsides. The NCERT textbook does not list Cynodon among invasive alien species. In fact, it is often used in traditional medicine and as a hardy ground cover precisely because it is well-adapted to local conditions.

Therefore, the odd one out is Cynodon.

Check each option against the specific named-species list the chapter gives for Indian invasive aliens (Parthenium, Lantana, Eichhornia) — three match directly; Cynodon (doob/Bermuda grass) is absent from that list and is in fact a native Indian grass, so it's identified by exclusion, not by any property of being 'aggressive' in a lawn.