Given that
$$\alpha_1$$ = nozzle angle
n = number of rows of moving blades, in a velocity compounded impulse turbine, the optimum blade speedratio is

A

$$2 \cos \alpha_1 n$$

B

$$\frac{n \cos \alpha_1}{2}$$

C

$$\frac{\cos \alpha_1}{2(n + 1)}$$

D

$$\frac{\cos \alpha_1}{2n}$$