What causes the wind to deflect toward the left in the Southern hemisphere?

Answer: (c) Rotation of the earth

The Earth’s rotation (Coriolis effect) deflects winds to the left in the southern hemisphere.

The idea

The Coriolis effect is the apparent turning of motion viewed from rotating Earth. Deflection is to the right of motion in the Northern Hemisphere and to the left in the Southern Hemisphere. It acts on moving air rather than starting the wind. A pressure difference supplies the initial driving force.

Pressure difference sets air moving → Earth rotates beneath the moving air → Motion is viewed in Earth’s rotating frame → Southern Hemisphere motion bends left → Wind direction differs from a straight pressure-gradient path

Why the others are wrong

(b) The magnetic field doesn’t steer winds.

(d) Pressure drives winds but doesn’t deflect them.

Elimination technique

Pressure drives air from high to low pressure; the question asks what turns that motion. Earth’s rotation provides the deflection, while the magnetic field does not steer ordinary winds.

Also know

Coriolis is zero at the equator and strengthens towards the poles for a given speed. It also affects ocean currents and large-scale moving water. A wind is named for the direction it comes from. Earth’s revolution around the Sun governs the year; rotation governs the day and this deflection.