Question

why is high pressure prevalent in Polar regions​

Answer 1

The cold temperatures in the polar regions cause air to descend to create the high pressure (a process called subsidence), just as the warm temperatures around the equator cause air to rise to create the low pressure intertropical convergence zone.

Answer 2

The cold temperatures in the polar regions cause air to descend to create the high pressure  just as the warm temperatures around the equator cause air to rise to create the low pressure intertropical convergence zone.