A nation runs a trade surplus when d) it lends more than it borrows. This means that the value of the goods and services it sells to other countries exceeds the value of what it buys from them, indicating that more money is flowing into the country than out.
To break it down further, a trade surplus occurs when exports surpass imports. While options a, b, and c present conditions that might describe a different economic scenario, option d directly correlates to a trade surplus as it signifies that the country is investing more abroad than it is borrowing to finance its own consumption and investment.