问题如下：
Which of following is not a reason that why differences between equity reported on the balance sheet and market value of equity exist:
选项：
A.Most of Assets and liabilities reported on balance sheet are measured by historical costs.
B.The factors affect market value of equity are also included on balance sheet.
C.The market value of equity is updated continuously, but equity on B/S is not.
解释：
B is correct. Some factors affect market value of equity, but they are not reported on balance sheet.
请问a为什么不对？
