In centrifugal compressors,. There is a tendency of increasing surge when

Question

Consider the follow statements:

In centrifugal compressors,. There is a tendency of increasing surge when

1. The number of diffuser vanes is less than the number of impeller vanes.                              
2. The number of diffuser vanes is greater than the number of impeller vanes.
3. The number of diffuser vanes is equal to the number of impeller vanes.
4. Mass flow is greatly in excess of that corresponding to the design mass flow.

Which of these statements is/are correct?

1. 1 and 4                        (b) 2 alone

(c) 3 and 4                         (d) 2 and 4