Step 1: Determine Kanayi Kunhiraman's primary works and their materials. He is known for large outdoor concrete sculptures.
Step 2: Evaluate the provided choices.
(C) The Conch (Shankum): A large concrete sculpture at Veli Tourist Village, Thiruvananthapuram.
(D) Sagarakanyaka (The Mermaid): A large, 35m concrete sculpture at Shankumugham Beach, Thiruvananthapuram.
Both (C) and (D) are well-known, large concrete works by the artist. (A) and (B) are not major concrete sculptures by him.
Step 3: Select the correct combination. The answer is (C) and (D).