A simile is a figure of speech that directly compares two things. It uses the words 'as...as' and 'like' in its comparison.
Option D: The sentence compares two things with one another, the 'scarf' with the 'feather', and it contains the word 'as...as': the scarf is light, like a feather.
Hence, it displays a simile and option D is correct.
Option A: This sentence states an action 'deer darted through the grass' and does not express any comparison.
Option B: 'This statement, too, states an action 'the sun shone bright'.
Option C: This sentence states an action 'they were frozen with fear'.
These options do not show any comparison and hence don't express a simile.
Hence, options A, B and C are wrong.