问题如下：
Beta Investment Corporation claims to comply with the GIPS standards. On 18 May, the firm received a notification of a portfolio’s termination. When should the portfolio be removed from the composite if composite returns are calculated monthly?
选项：
A.30 April
B.18 May
C.31 May
解释：
A is correct.
考点：3.A Composite construction-3.A.6
解析：条款3.A.6 Terminated portfolios must be included in the historical performance of the composite up to the last full measurement period that each portfolio was under management
终结的组合必须被包含记录在Composites的历史业绩中，过去的历史业绩必须持续记录至该组合上一个完整的业绩评估周期结束为止。
18 May的last full measurement period是4月，所以在四月底，也就是4月30日把这个portfolio移除。
4月底把portfolio移除，但是相关历史业绩还是一直都保持的吧？
如果是按年计算，就是在上年12月31日止的时点，把portfolio移除吗？
