Which of the following statements is/are true in case of one-dimensional flow of perfect gas through a converging diverging nozzle?
1. The exit velocity is always supersonic
2. the exit velocity can be subsonic or supersonic
3. If the flow is isentropic, the exit velocity must be supersonic
4. If the exist velocity is supersonic, the flow must be isentropic
Select the correct answer using the codes given below:
a. 2 and 4 b. 2, 3 and 4
c. 1, 3 and 4 d. 2 alone