In a turbo- jet engine, thrust may be increased by

Question

 Consider the following statements:

In a turbo- jet engine, thrust may be increased by   

1. Increasing the jet velocity
2. Increasing the mass flow rate of sir.
3. After burning of the fuel.

Which of these statements are correct?

(a) 1 and 2                   (b)2 and 3

(c) 1 and 3                   (d)1,2 and 3