Commensalism is a type of symbiotic relationship between organisms in which one organism benefits without harming the other.
Many birds form a commensal relationship with some species of ants like the army ants. A great number of army ants trail on the forest floor, and while moving, stir up many insects lying in their path. The birds follow these army ants and eat up the insects that try to escape from them. The birds benefit by catching their prey easily, while the army ants are totally unaffected.

Flora and Fauna of Bhitarkanika National Park
Flora: Mangrove species, casuarinas, and grasses like the indigo bush.
Fauna: The Park is home to the saltwater crocodile, Indian python, black ibis, wild boar, rhesus monkey, chital, darter, cobra, monitor lizard. Olive ridley turtles’ nest on Gahirmatha and other nearby beaches. Bhitarkanika has one of the largest populations of saltwater crocodile in India.

1, 2 and 4 are correct.
The red-headed vulture also known as the Asian king vulture, Indian black vulture or Pondicherry vulture, is an Old World vulture mainly found in the Indian subcontinent, with small disjunct populations in some parts of Southeast Asia.
Flying squirrel, (tribe Pteromyini), any of more than 50 species of gliding squirrels. Three species are North American, two live in northern Eurasia, and all others are found in the temperate and tropical forests of India and other parts of Asia.
Gee’s golden langur (Trachypithecus geei), also known as simply the golden langur, is an Old World monkey found in a small region of western Assam, India and in the neighbouring foothills of the Black Mountains of Bhutan. The Koala is an arboreal herbivorous marsupial native to Australia.

Only statement 2 is correct.
Statement 1: They have adapted to desert conditions by developing extremely long root systems to draw water from deep underground near the water table. The mesquite’s roots are considered the longest of any desert plant and have been recorded as long as 80 feet.
Statement 2: Some have succulent leaves to store moisture. Some have thorny leaves to reduce water loss by transpiration. Waxy leaves protect soil moisture beneath the coating.

2 and 3 are correct.
India’s soil biodiversity is in grave peril, according to the Global Soil Biodiversity Atlas prepared by the World Wide Fund for Nature.
The WWF’s ‘risk index’ for the globe — indicating threats from loss of above-ground diversity, pollution and nutrient over-loading, over-grazing, intensive agriculture, fire, soil erosion, desertification and climate change — shows India among countries whose soil biodiversity faces the highest level of risk. Soil biodiversity encompasses the presence of micro-organisms, micro-fauna (nematodes and tardigrades for example), and macro-fauna (ants, termites and earthworms).