Problem 7. True or false? Please motivate your answers. (a) The curve with parametric equations r = tcos(t), y = tsin(t), z = t lies on the surface z? = x2 + y?. (b) The curve r(t) = (t3, 213, 313) is a line. (c) Let r(t) be a parametrizationch that r'(t) exists and is contin- uous. Then # |r(t)| = [r'(t)|