Ok, I understand why C is correct. But why is A wrong? As holo-RBP: STRA6 increases (meaning holo-RBP increases even with constant STRA6), relative retinol fluorescence increases. And according to the graph, at 4holo-RBP (higher ratio), it has a higher relative retinal fluorescence. (is there something wrong with the phrasing of STRA6-catalyzed?