Solar radiation, heat balance and temperature

The main reason that the earth experiences highest temperatures in the
subtropics in the northern hemisphere rather than at the equator is :
(a)
Subtropical areas tend to have less cloud cover than equatorial areas.
(b)
Subtropical areas have longer day hours in the summer than the
equatorial.
(c)
Subtropical areas have an enhanced “green house effect” compared
to equatorial areas.
(d)
Subtropical areas are nearer to the oceanic areas than the equatorial
locations.