What explains the eastward flow of the equatorial counter-current?

The correct answer is B. The equatorial counter-current flows eastward, against the westward-moving North and South Equatorial currents, in the narrow band between them. Trade winds push both equatorial currents westward, and where they converge, water piles up in the middle. This creates a slight surface slope, and gravity pulls the excess water back eastward along the equator. That piling-up mechanism is the core idea.

Why the others fail:

• A: Earth's rotation causes the Coriolis deflection that shapes gyres, but Coriolis is nearly zero at the equator, so it cannot reverse the flow there.
• C: Salinity differences drive deep thermohaline circulation, which is slow and not a surface eastward current on the equator.
• D: A belt of calm (the doldrums) has weak winds. Calm does not push water. The counter-current comes from convergence and wind-driven accumulation, not from the absence of wind.

Concept: wind-driven surface circulation and the sea-surface slope it creates. For Mains GS-I (Geography, oceans and climate), this links to how monsoon winds shape surface currents in the Indian Ocean.

Trap: Students pick A because Earth's rotation explains most ocean gyres, but on the equator the Coriolis effect is almost zero.