For calculating the allowable stress of long columns $${\sigma _0} = \frac{{{\sigma _y}}}{n}\left[ {1 - a{{\left( {\frac{1}{r}} \right)}^2}} \right]$$    is the empirical formula, known as

A. $$\frac{2}{3}$$ B. $$\frac{3}{2}$$ C. $$\frac{5}{8}$$ D. $$\frac{8}{5}$$

A. Normal stresses only B. Tangential stresses only C. Normal stresses as well as tangential stresses D. None of these

A. $$\frac{{\text{M}}}{{\text{I}}} = \frac{{\text{R}}}{{\text{E}}} = \frac{{\text{F}}}{{\text{Y}}}$$ B. $$\frac{{\text{I}}}{{\text{M}}} = \frac{{\text{R}}}{{\text{E}}} = \frac{{\text{F}}}{{\text{Y}}}$$ C. $$\frac{{\text{M}}}{{\text{I}}} = \frac{{\text{E}}}{{\text{R}}} = \frac{{\text{F}}}{{\text{Y}}}$$ D. $$\frac{{\text{M}}}{{\text{I}}} = \frac{{\text{E}}}{{\text{R}}} = \frac{{\text{Y}}}{{\text{F}}}$$

A. $$\frac{{\text{M}}}{{\text{T}}}$$ B. $$\frac{{\text{T}}}{{\text{M}}}$$ C. $$\frac{{2{\text{M}}}}{{\text{T}}}$$ D. $$\frac{{2{\text{T}}}}{{\text{M}}}$$