Consider the following statements regarding laminar sub layer of boundary layer flow
1. The laminar sub layer exists only in a region that occurs before the formation of laminar boundary layer
2. The laminar sub layer is a region next to the wall where the viscous force is predominant while the rest of the flow is turbulent
3. The laminar sub layer occurs only in turbulent flow past a smooth plate Which of the statements given above is/are correct?
a. 1, 2 and 3 b. 1 and 2
c. only 2 d. 1 and 3