Which of the Following Statements Is Always True

Multiple Choice

Which of the following statements is always true?

A) If f is continuous at c, then it must be differentiable at c.
B) If f is differentiable at c, then it must be continuous at c.
C) If f is not differentiable at c, then it must be discontinuous at c.
D) If f(c + h) = f(c) , then f must be differentiable at c.
E) All of the above