According to the second paragraph, the formation of the Atlantic Ocean is the example of________.

A．It gives a general introduction to some of the most famous realistic writers in last century.
B．It mainly reviews the difference between the fictional world in Oates's novels and the real world.
C．It outlines the career life of Joyce Carol Oates, one of the most famous American writers.
D．It focuses on the writing style of some famous realistic American writers.

A．can be classified into two types
B．is formed along the margins of the plates
C．consists of semi-molten rocks
D．is about 70 to 100 kilometers thick