问题如下：
For periods beginning on or after 1 January 2010, which of the following is incorrect? The portfolio must be valued:
选项：
A.on the date of all large cash flows
B.at the last business day of the month rather than the calendar month-end
C.no more frequently than required by the valuation policy
解释：
B is correct.
考点：1 input data-1.A.3 and 1.A.4
解析：
Portfolios must be valued:
1.A.3 b For periods beginning on or after 1 January 2010, on the date of all large cash flows（A选项描述正确）
1.A.3.c No more frequently than required by the valuation policy（C选项描述正确）
1.A.4 For periods beginning on or after 1 January 2010, firms must value portfolios as of the calendar month end or the last business day of the month.（自2010年1月起，公司必须在日历月的结束日对组合做出估值计算，如果该日没有相应的市场价格，例如周六周日闭市，那么就在该月最后一个营业日计算估值。B描述错误，不是rather than而是or。）
意思是最后一日如果是周六日，那么就以最后一个营业日作为结算日，那B不应该是正确的么？
