Explanations:The question asks about the common international border shared by the states of Uttarakhand, Uttar Pradesh, Bihar, and Sikkim. To understand the correct answer, it is essential to have a clear understanding of the geographical layout of these states and their neighboring countries.
Uttarakhand, Uttar Pradesh, Bihar, and Sikkim are all located in the northern and eastern parts of India. Among the given options, Nepal is the only country that shares a border with all these states. Nepal is a landlocked country located in South Asia, and it is bordered by India to the south, east, and west, and by China to the north.
Uttarakhand shares a border with Nepal in the north and northwest. Uttar Pradesh, which is the largest state in India by population, also shares a border with Nepal in the north. Bihar, located in the eastern part of India, shares a border with Nepal in the north and northwest. Sikkim, a small state in the northeastern part of India, shares a border with Nepal in the west and northwest.
China, on the other hand, shares a border with Uttarakhand and Sikkim but not with Uttar Pradesh or Bihar. Bhutan shares a border with Sikkim but not with the other three states. Myanmar, located in Southeast Asia, shares a border with the northeastern states of India but not with the states mentioned in the question.
Therefore, the correct answer is Nepal, as it is the only country that shares a common border with all the mentioned states. This question tests the geographical knowledge of the borders of Indian states and their neighboring countries, which is crucial for competitive examinations and general geographical awareness.