According to the provided answer, the largest trading partner of India in external trade for the year 2015-2016 is China.
Option 1: The United States of America (USA) is a major trading partner for India but not the largest in the year 2015-2016.
Option 2: The United Kingdom (UK) is also an important trading partner for India, but it is not the largest for the mentioned year.
Option 3: The United Arab Emirates (UAE) has significant trade relations with India but is not the largest trading partner for the mentioned year.
Option 4: China is the correct answer as it was the largest trading partner of India in external trade for the year 2015-2016. China and India have a substantial bilateral trade relationship with various goods and services being exchanged between the two countries.
Therefore, the correct answer is option 4, China.