Option 1 -> Starts with (A) which lacks context, ending with incomplete (D) phrase "not only do" - grammatically incorrect.
Option 2 -> Places (B) directly after (D), breaking the "not only do" construction - doesn't flow logically.
Option 3 -> Follows proper structure: (D) introduces conditional clause with "when pollution levels rise, not only do", followed by (A), (C), (B) completing the "not only...but also" pattern.
Option 4 -> Begins with (C) "with worsening symptoms, they also see healthy" which lacks proper subject introduction - grammatically flawed.
Hence, Option 3: (D), (A), (C), (B) -> This forms the coherent sentence: "When pollution levels rise, not only do doctors see a spike in their patients with respiratory diseases coming in with worsening symptoms, they also see healthy people complaining of cough, wheezing and breathlessness." It correctly uses the "not only...but also" construction to show two effects of rising pollution levels. -> correct