(A) Build castles in the air → To have unrealistic dreams - imagining impossible or fanciful scenarios
(B) Count your chickens before they are hatched → To assume success too soon - making plans based on expected outcomes that haven't occurred yet
(C) Walk on eggshells → To be very careful in a sensitive situation - acting cautiously to avoid conflict or upset
(D) Swim against the tide → To go against popular opinion - choosing to oppose mainstream views or trends
Hence, Option 3: (A) - (IV), (B) - (I), (C) - (II), (D) - (III) → This correctly matches all four idioms with their appropriate meanings, demonstrating proper understanding of common English expressions used in both formal and informal communication → correct