How Many Real Roots Does the Equation $x^{5}-7 x+c=0$ Have in the Interval

Multiple Choice

How many real roots does the equation $x^{5}-7 x+c=0$ have in the interval $[-1,1]$ ?

A) at most five real roots
B) no real roots
C) at most one real root
D) at most two real roots
E) at most three real roots