Vultures which used to be very common in Indian countryside some years ago are rarely seen nowadays. This is attributed to

Explanation

Option (b) is correct. Vultures in India have declined dramatically due to the ingestion of diclofenac, a drug used to treat cattle. This drug causes kidney failure and visceral gout in vultures that consume the carcasses of treated animals. Despite the ban, illegal use continues, leading to a significant drop in vulture populations.