Option 4: (D), (C), (A), (B) → This creates a logical flow: "The human brain contains around 86 billion neurons that communicate constantly enabling thoughts, emotions, and bodily functions making it the body's control centre" - starts with the subject (brain), follows with description (neurons), explains their function (enabling thoughts/emotions), and concludes with the result (control centre) → correct
The other options create grammatically incorrect or illogical sentence structures that either start awkwardly with dependent clauses or fail to establish proper subject-verb relationships.
Hence, Option 4: (D), (C), (A), (B) → The sentence flows naturally from introducing the brain and its neurons, to explaining what they enable, to concluding why it's the control centre → correct