The correct option is D b a c d
A sentence is made up the basic parts: subject (doer of the action) +
verb (describing the action) + object (receiver of the action).
The object may or may not be a part of a sentence. Also, there are various elements that modify these parts.
The correct form of the given sentence is:
Birds of a feather (subject)/ flock (verb)/ together (adverb).
b a c d
'Birds of a feather flock together' is a proverb that means:
People who have the same tastes or interests will be found together.
Hence option D 'b a c d' is correct.
Options A, B and C are incorrect because they do not create sentences that follow the required structure.