Step 1: Identify Kanayi Kunhiraman's major works and their material. He is well-known for his large-scale outdoor sculptures, often made of concrete.
Step 2: Analyze the given options.
(C) The Conch (Shankum): A massive concrete sculpture located at Veli Tourist Village in Thiruvananthapuram.
(D) Sagarakanyaka (The Mermaid): A gigantic, 35m long concrete sculpture located at Shankumugham Beach in Thiruvananthapuram.
Both (C) and (D) are famous, monumental concrete works by the artist. (A) and (B) are not his widely recognized major concrete sculptures.
Step 3: Conclude the correct combination. The correct answer is (C) and (D).