$${D_8}\,{D_1}\, + {D_4}\,{D_2}\, + \,\overline {{D_8}} \,{D_2}\,{D_1}$$

$${D_8}\,{D_1}\, + {D_4}\,{D_2}\,\overline {{D_1}} \, + \,\overline {{D_4}} \,{D_2}{D_1} + \overline {{D_8}} \,\overline {{D_4}} \,\overline {{D_2}} \,\overline {{D_1}} \,$$

$${D_8}\,{D_1}\, + \,{D_4}\,{D_2}\, + \,\overline {{D_8}} \,\overline {{D_4}} \,\overline {{D_2}} \,\overline {{D_1}} \,$$

$${D_4}\,{D_2}\,\overline {{D_1}} \, + \,{D_4}\,{D_2}\,{D_1}\, + \,{D_8}\,\overline {{D_4}} \,{D_2}{D_1}$$

Both (i) and (ii)

Both (i) and (iii)

Only (iii)

Only (ii)

2$$^n$$

$${2^2}^n$$

2$$^{n - 1}$$

2$$^{n + 1}$$

Guided wavelength is never less than the free space wavelength

Wave impedance is never less than the free space impedance.

Phase velocity is never less than the free space velocity

TEM mode is possible if the dimensions of the wave guide are properly chosen.