The velocity triangles at the inlet and exit of the rotor of a turbomachine are shown. $V$ denotes the absolute velocity of the fluid, $W$ denotes the relative velocity of the fluid and $U$ denotes the blade velocity. Subscripts $1$ and $2$ refer to inlet and outlet respectively. If $V_2 =W_1$ and $V_1=W_2$, then the degree of reaction is
- $0$
- $1$
- $0.5$
- $0.25$