What causes global convection currents to form

if you have these answers,

A. Differences in elevation on earth

B. Earths local winds

C. Unequal heating of earths surface

D. Earths spin

The answer is C. Unequal heating of earths surface (Apex)

Wind is the level development of air. All breeze is caused by the uneven warming of Earth's surface, which gets global convection currents or streams under way. Convection streams on a huge scale cause worldwide breezes; convection ebbs and flows on a little scale cause nearby breezes.