【单选题】

The primary function of the passage as a whole is to
A．(A) introduce a new explanation of a physical phenomenon

B．(B) explain how a physical phenomenon is measured and described
C．(C) illustrate the limitations of applying mathematics to complicated physical phenomena
D．(D) indicate the direction that research into a particular physical phenomenon should take
E．(E) clarify the differences between an old explanation of a physical phenomenon and a new model of it