An economically important tree species in Nagaland, known for its timber, is:

Eucalyptus
Teak
Pine
Hollong

The correct answer is: d) Hollong

Hollong (Dipterocarpus macrocarpus) is a large tree species found in the Eastern Himalayas, including Nagaland. It is an economically important tree species, known for its timber. The wood is used for construction, furniture, and other purposes. Hollong is also a source of resin and gum.

Eucalyptus is a genus of flowering plants in the myrtle family, Myrtaceae. The genus is native to Australia, with over 700 species. Eucalyptus trees are fast-growing and have a wide range of uses, including timber, paper, and fuel. However, eucalyptus is not native to Nagaland and is not an economically important tree species there.

Teak is a large tree species in the family Dipterocarpaceae. The tree is native to tropical and subtropical Asia, including India, Myanmar, Thailand, and Malaysia. Teak is an economically important tree species, known for its durable wood. The wood is used for construction, furniture, and other purposes. Teak is not native to Nagaland and is not an economically important tree species there.

Pine is a genus of coniferous trees in the family Pinaceae. The genus is native to the Northern Hemisphere, with over 100 species. Pine trees are important for their timber, resin, and turpentine. However, pine is not native to Nagaland and is not an economically important tree species there.