Mach number is defined as the ratio of the local flow velocity to the sonic velocity in the fluid. For what value of Mach number, the gases are considered incompressible?

A. Thermal conductivity B. Electrical conductivity C. Specific gravity D. Electrical resistivity

A. $$\frac{{\text{V}}}{{{{\text{V}}_{\max }}}} = {\left( {\frac{{\text{x}}}{{\text{r}}}} \right)^{\frac{1}{7}}}$$ B. $$\frac{{\text{V}}}{{{{\text{V}}_{\max }}}} = {\left( {\frac{{\text{r}}}{{\text{x}}}} \right)^{\frac{1}{7}}}$$ C. $$\frac{{\text{V}}}{{{{\text{V}}_{\max }}}} = {\left( {{\text{x}} \times {\text{r}}} \right)^{\frac{1}{7}}}$$ D. None of these

A. d B. $$\frac{1}{{\text{d}}}$$ C. $$\sigma $$ D. $$\frac{l}{\sigma }$$

A. $$\frac{{4\pi {\text{g}}}}{3}$$ B. $$\frac{{0.01\pi {\text{gH}}}}{4}$$ C. $$\frac{{0.01\pi {\text{gH}}}}{8}$$ D. $$\frac{{0.04\pi {\text{gH}}}}{3}$$