A turn ocean currents and storm systems clockwise in the Northern Hemisphere, but what is appearing as a force is just the inertia of the matter that obeys
"is appearing" is in conflict with the "turn", also, no real reason to use ing form here
B in the Northern Hemisphere turn ocean currents and storm systems clockwise, but what appears to be a force, just the inertia of the matter, obeys
"what" = C. Effect, it is not the Effect that obeys, it is the inertia that obeys. More importantly, the point of the original sentence is: it is not a force, but rather an inertia
C turn ocean currents and storm systems in the Northern Hemisphere clockwise, that appear as a force, and that is just the inertia of the matter, which obeys
no complete sentence here
D turn ocean currents and storm systems clockwise in the Northern Hemisphere, but what appears as a force is just the inertia of the matter obeying
CorrectE have turned ocean currents and storm systems clockwise in the Northern Hemisphere, and that is just the inertia of the matter that appears as a force obeying
The sentence is describing a general pattern, therefore should not use "have turned".