Proteins are the building blocks (A) of immune cells, and adequate protein intake (B) is necessary for a response (C) immune robust (D).

Explanation

Among the highlighted words, “response” and “robust” are incorrectly placed. The correct combination of words that should replace each other in order to make the sentence grammatically and contextually correct is C-D. The word “response” should be replaced with “robust” as the given statement is saying that proteins serve as essential components for building immune cells, and maintaining sufficient protein intake is crucial for a strong and effective immune response. So, the correct sentence after rearrangement of words would be, “Proteins are the building blocks (A) of immune cells, and adequate protein intake (B) is necessary for a robust (D) immune response (C).”