Answer: c. occur gradually over millions of years.
Explanation:
Lithospheric plates exist under the surface of the earth that we see and form part of the earth's crust. They rest on the mantle which is very hot and as a result of this temperature, these plates are always moving.
These movements however occur gradually over millions of years which is why we do not notice it happening but these plate movements are very influential as they lead to the production of various land masses such as mountains when the movements lead to the plates colliding.
It is a sentence that contains both an independent clause and one or more subordinate clauses
