In the $3-$D motion of the fluid, the component of rotation about z$-$axis is given by

a$)\frac{1}{2}(\frac{\text{d}\text{e}\text{l}\text{u}}{\text{d}\text{e}\text{l}\text{z}}-\frac{\text{d}\text{e}\text{l}\text{w}}{\text{d}\text{e}\text{l}\text{x}})$

b$)\frac{1}{2}(\frac{\text{d}\text{e}\text{l}\text{v}}{\text{d}\text{e}\text{l}\text{x}}-\frac{\text{d}\text{e}\text{l}\text{u}}{\text{d}\text{e}\text{l}\text{y}})$

c$)\frac{1}{2}(\frac{\text{d}\text{e}\text{l}\text{w}}{\text{d}\text{e}\text{l}\text{y}}-\frac{\text{d}\text{e}\text{l}\text{v}}{\text{d}\text{e}\text{l}\text{z}})$

d$)\frac{1}{2}(\frac{\text{d}\text{e}\text{l}\text{v}}{\text{d}\text{e}\text{l}\text{y}}-\frac{\text{d}\text{e}\text{l}\text{u}}{\text{d}\text{e}\text{l}\text{x}})$