A curve C is defined by the parametric equations x(t)=f(t) and y(t)=t, where f is a differentiable function. Which of the following gives the length of curve C from t=−1 to t=8 ? All answers are integrated from -1 to 8

A= √(f(t)+t dt)
B= √(((f(t))^2)+t^2 dt)
C= √(f'(t)+1 dt)
D= √(((f'(t))^2)+1 dt)