Final answer:
Option D, asserting that surface currents are driven by density differences in the water, is not true. Surface currents are primarily driven by wind and Earth's rotation, which moves heat across the planet.
Step-by-step explanation:
The statement about surface currents that is NOT true is: D. They are driven by density differences in the water. This statement is incorrect because surface currents are primarily driven by wind and the rotation of the Earth, known as the Coriolis effect, rather than density differences. The flow of surface currents can form gyres and are major transporters of heat across Earth's surface, distributing thermal energy from warmer to cooler areas.