A incidência de raios solares está muito mais presente na região equatorial do que nos pólos, portanto, há um maior aquecimento dos oceanos nesta região, enquanto que perto dos pólos há um maior resfriamento.
Because of Earth's axial tilt (obliquity), our planet orbits the Sun on a slant which means different areas of Earth point toward or away from the Sun at different times of the year. Around the June solstice, the North Pole is tilted toward the Sun and the Northern Hemisphere gets more of the Sun's direct rays.
Its all depends on were you're starting. If you're starting from a bob cut or a pixie your hair might take longer than others to grow.
It also depends on your diet. If what you eat is balanced with fruit, vegetables, protein and calcium, that should help your hair grow. Iron and vitamin D also helps too.
:)
I find that the best answer is the following one:
c. determined by factors outside our control
For example, even though life is very hard in the very hot and the very cold regions, we can't control it: so this is an example of a physical environment that is hard to control.
In comparison, it is often easier to describe than our social environment.