What do we mean by the diffraction limit of a telescope?

Question

a)It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.
b)It is the maximum size to which any telescope can be built.
c)It describes the maximum exposure time for images captured with the telescope.
d)It describes the farthest distance to which the telescope can see.

Answer 1

a) It is the best resolution a given size telescope can achieve due to the wave nature of light.

Answer 2

a is correct coz diffraction limit is nothin else than resolving power of a telescope which is the ability of it to distinguish two closely lying objects in absense of atmospheric distortion.