The following are multiple choice questions (with answers) about medical knowledge.   **Question:** A researcher is conducting an experiment on the mouse kidney to study the relative concentrations between the tubular fluid and plasma of a number of substances along the proximal convoluted tubule. Based on the graph shown in figure A, which of the following best describes the tubular fluid-to-plasma concentration ratio of urea?   (A) B   (B) C   (C) D   (D) E
['(A) B <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) B \n (B) C \n (C) D \n (D) E <> possible answers', '  A researcher is conducting an experiment on the mouse kidney to study the relative concentrations between the tubular fluid and plasma of a number of substances along the proximal convoluted tubule. Based on the graph shown in figure A, which of the following best describes the tubular fluid-to-plasma concentration ratio of urea? <> context@']