(1 point) Which of the following distributions is suitable to model the length of time that elapses before the first telephone call is received by a switchboard? A. Uniform B. Poisson C. Normal D. Exponential Which of the following is always true for all probability density functions of continuous random variables? A. They are bell-shaped B. The Prea under the curve is 1.0 C. They are symmetrical D. They have the same height.