Solution
Option 1 -> External commercial borrowings are autonomous transactions undertaken for profit or business expansion purposes.
Option 2 -> Exports are autonomous transactions driven by the motive to earn profit through international trade.
Option 3 -> Official reserve transactions are accommodating transactions, not autonomous, as they are undertaken by central banks to correct BOP imbalances.
Option 4 -> Foreign direct investment is an autonomous transaction motivated by investment returns and business expansion.
Hence, Option 3: official reserve transactions -> Autonomous transactions are independent transactions undertaken due to profit motive, consumption, or investment needs. Accommodating transactions (like official reserve transactions) are undertaken specifically to finance deficits or surpluses in the balance of payments. When there's a BOP deficit or surplus, the central bank uses official reserves to balance it, making these transactions dependent on the BOP position rather than independent economic motives. -> correct