I would like to know when they say in this website (http://wiki.backyardbrains.com/Exper...e_Faraday_Cage)

*One rule of thumb often used for Faraday cages to prevent transmission is that the holes need to be no larger than 1/10 of the wavelength of the signal*

I would like to know what does it really mean out of these 5 options?

a) we need a hole smaller that a square hole whose sides =1/10 of the wavelength to prevent propagation

b) we need a hole smaller than a rectanglar hole which has one side = 1/10 of the wavelength to prevent propagation

c) we need a hole smaller than a square hole whose diameter = 1/10 of the wavelength to prevent propagation

d) we need a hole smaller than a circle hole whose diameter = 1/10 of the wavelength to prevent propagation

e) the perimeter of the hole has to be smaller than 1/10 of the wavelength to prevent propagation

Thank you