Original sentences

a measurable physical difference in the ocean occurs at this point. the water surrounding the antarctic continent is considered an ocean unto itself.

new sentence

because a measurable physical difference in the ocean occurs at this point, the water surrounding the antarctic continent is considered an ocean unto itself.

which choice shows the type of change used on the original sentences to create the new one?

a.
subordinate clause with subordinating conjunction “because”

b.
combined using a compound object

c.
subordinate clause with coordinating conjunction “because”

d.
combined using a compound subject