The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Supragingival plaque undergoes which of the following changes with time?   (A) Plaque mass decreases   (B) Plaque microflora becomes more gram positive   (C) Plaque microflora becomes gram negative   (D) Plaque microflora becomes predominantly spirochetal
['(C) Plaque microflora becomes gram negative <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Plaque mass decreases \n (B) Plaque microflora becomes more gram positive \n (C) Plaque microflora becomes gram negative \n (D) Plaque microflora becomes predominantly spirochetal <> possible answers', '  Supragingival plaque undergoes which of the following changes with time? <> context@']