Diffraction - opening smaller than wavelength

Hi! I have this problem:

1. The problem statement, all variables and given/known data

Which combination will produce the least degree of diffraction?

A. λ of 2.0m through an opening of 1.0 cm

B. λ of 30m through an opening of 2.0 m

C. λ of 2.0m through an opening of 25 m

D. λ of 5.0nm through an opening of 45 m



3. The attempt at a solution



I know that the answer would be D because the wavelength is so much smaller than the opening that it would barely diffract, and that C would also be pretty low.



What I'm not sure of is what happens with A and B. If the wavelength is much greater than the opening, does that mean it will not be able to go through it, or does that mean it will go through and diffract a lot?





thanks for your time!