Which one of the following countries joined India and USA in the Malabar naval exercise held in July 2017?

The correct answer is A) Japan. The Malabar exercise of July 2017 was a trilateral drill among India, the United States and Japan, held in the Western Pacific. Japan had become a regular participant after its 2015 entry, which is why the 2017 edition is remembered as a three-nation exercise.

• South Korea has never been a Malabar participant. Its naval ties with India run through separate bilateral engagements.
• France has taken part in other Indian Ocean exercises with India, but not in Malabar 2017.
• Philippines is a US treaty ally and a Southeast Asian partner, but it was not part of Malabar 2017.

The core concept is the Quad-linked naval grouping and India's maritime diplomacy in the Indo-Pacific. For Mains GS-II (India and its neighbourhood) and GS-III (security), this links to the South China Sea, freedom of navigation and the balance of power. Australia's later full participation (2020) is a separate development and is not relevant to the 2017 question.

Trap: Aspirants often pick Australia or the Philippines because they are the usual Indo-Pacific partners. Remember that Malabar 2017 was India, US and Japan.