Which one of the following is not responsible for the extinction of a species ?

The answer is A) Broad niche. A broad niche means the species can use many resources and tolerate a range of habitats and conditions, so it can absorb environmental change. That buffering is why generalists tend to survive while specialists are more likely to vanish.

Why the other options are causes of extinction:

• Narrow niche (C): Specialists depend on a few resources or conditions. If those disappear, the species has no fallback. The giant panda's bamboo dependence is a familiar example.
• Large body size (B): Large animals need more food and space, usually breed slowly, and have small populations. They are hit harder by habitat loss and hunting. This is why megafauna were among the first casualties of late Quaternary extinctions.
• Lack of genetic variability (D): Without variation, a population cannot adapt to new diseases or climate shifts, and inbreeding depression reduces fitness.

The core concept is the niche breadth and extinction vulnerability link, which connects to the Environment and Ecology syllabus and to Mains questions on biodiversity loss and conservation strategy.

Trap: Many aspirants read "broad" as "weak" and pick the option that sounds less favourable. Generalist species are the ones more likely to survive.