The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Hardness of stone surface is affected by?   (A) Impression wax   (B) Impression compound   (C) Hydrocolloid impression material   (D) Rubber based material
['(C) Hydrocolloid impression material <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Impression wax \n (B) Impression compound \n (C) Hydrocolloid impression material \n (D) Rubber based material <> possible answers', '  Hardness of stone surface is affected by? <> context@']