Which forest also known as the 'lungs of the planet earth' ?

The correct answer is Option (1) → Amazon rain forest

Option (1) Amazon rain forest — Correct. Of the options, only the Amazon rain forest bears this name in NCERT, because of its huge size.

Option (2) Rain forest of north-east India — Incorrect. It is rich in species, but NCERT gives the name to the Amazon.

Option (3) Taiga forest — Incorrect. The taiga is the coniferous forest of cold northern regions, with far fewer species.

Option (4) Tundra forest — Incorrect. The tundra is a treeless, cold region of the far north.

NCERT Extract:
Loss of Biodiversity – “… The Amazon rain forest (it is so huge that it is called the ‘lungs of the planet’) harbouring probably millions of species is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle.”