Arunachal Pradesh shares its eastern border with:

The correct answer is: b) Myanmar.

Arunachal Pradesh is a state in northeastern India. It is bordered by Bhutan to the north, China to the east, Nagaland to the south, Assam to the southwest, and Sikkim to the west.

Myanmar, also known as Burma, is a country in Southeast Asia. It is bordered by China to the north, Laos to the northeast, Thailand to the east, Bangladesh to the west, India to the northwest, and the Andaman Sea to the southwest.

The other options are incorrect:

• Bhutan is a landlocked country in South Asia. It is bordered by China to the north and India to the south, east, and west.
• China is a country in East Asia. It is the world’s most populous country, with a population of over 1.4 billion. It is bordered by 14 countries, including Russia to the north, Mongolia to the northeast, North Korea to the east, South Korea to the southeast, Vietnam to the south, Laos and Myanmar to the southwest, India to the west, Bhutan and Nepal to the northwest, and Pakistan to the north.
• Bangladesh is a country in South Asia. It is bordered by India to the west, north, and east, and Myanmar to the southeast.