The correct answer is C. both (a) and (b).
Assam is a state in north-eastern India. It is the largest state in India by area, and the third most populous. The capital of Assam is Dispur.
The important industries of Assam are tea processing, oil refineries and coal, silk and plywood.
Tea processing is the largest industry in Assam. Assam is the world’s largest producer of black tea. The tea industry employs about 2 million people in Assam.
Oil refineries are also important in Assam. The state has two oil refineries, one at Digboi and the other at Numaligarh. The oil refineries produce gasoline, diesel, kerosene and other petroleum products.
Coal is another important industry in Assam. The state has large reserves of coal. The coal is used to generate electricity and to produce steel.
Silk and plywood are also important industries in Assam. Assam is the largest producer of silk in India. The silk industry employs about 1 million people in Assam. Plywood is made from wood. The plywood industry employs about 500,000 people in Assam.
The other options are incorrect. Option A is incorrect because it does not include silk and plywood. Option B is incorrect because it does not include oil refineries and coal. Option D is incorrect because it is not one of the important industries of Assam.