Passage: Arunachal Pradesh's gross state domestic product was estimated at US$706 million at current prices in 2004 and US$1.75 billion at current prices in 2012. Agriculture primarily drives the economy. Jhum, the local term used for shifting cultivation is being widely practised among the tribal groups, though owing to the gradual growth of other sources of income in the recent years, it is not being practised as prominently as it was earlier. Arunachal Pradesh has close to 61,000 square kilometres of forests, and forest products are the next most significant sector of the economy. Among the crops grown here are rice, maize, millet, wheat, pulses, sugarcane, ginger, and oilseeds. Arunachal is also ideal for horticulture and fruit orchards. Its major industries are rice mills, fruit preservation and processing units, and handloom handicrafts. Sawmills and plywood trades are prohibited under law. There are many saw mills in AP.Arunachal Pradesh accounts for a large percentage share of India's untapped hydroelectric potential. In 2008, the government of Arunachal Pradesh signed numerous memorandum of understanding with various companies planning some 42 hydroelectric schemes that will produce electricity in excess of 27,000 MW. Construction of the Upper Siang Hydroelectric Project, which is expected to generate between 10,000 and 12,000 MW, began in April 2009.

Question: what is the Arunachal's major grain industry?
rice