We use the Rayleigh criterion, which states that the minimum angular separation of two point sources such that ``an observer watching the images on the distant screen can just tell them apart" is, for a circular aperature with diameter ,
where is the wavelength of the light. %(See Bekefi and Barratt pages 578 and 579).
Plugging in the given value for and , we can find that
Therefore, answer (C) is correct.