Option 1: (A), (C), (D), (B) -> Starts with "water body" without introducing the subject first, making it grammatically incorrect.
Option 2: (B), (D), (C), (A) -> Begins with "connecting Asia, Africa, and Australia" which has no subject or context to connect to, creating a fragment.
Option 3: (C), (A), (D), (B) -> Forms a complete sentence: "The Indian Ocean is the third-largest water body covering about 20% of Earth's surface and serves as a major trade route connecting Asia, Africa, and Australia."
Option 4: (C), (B), (D), (A) -> Places "connecting Asia, Africa, and Australia" right after the subject, disrupting the logical flow of information.
Hence, Option 3: (C), (A), (D), (B) -> This sequence properly introduces the subject (Indian Ocean), describes it as the third-largest water body with its coverage area, mentions its function as a trade route, and concludes with its geographical location -> correct