Suppose that continuous random variable X follows an Exponential distribution with / = 2. Which of the following is the correct PDF graph? 0.9- 0.8+ 0.7+ 0.6+ O 0.5+ 0.4- 0.3 + 0.2+ 0.1 + 1 2 4 0.9 0.8 - 0.7 0.6+ O 0.5 + 0.4- 0.3+ 0.2+ 0.1 - -1 1 2 3 4 -0.1+