问题如下：
For periods beginning on or after 1 January, 2011, portfolios must be valued in accordance with:
选项：
A. the definition of fair value
B. the definition of cost
C. the principles of financial accounting
解释：
A is correct.
考点：1 input data-1.A.2
解析：条款1.A.2 For periods beginning on or after 1 January 2011, portfolios must be valued in accordance with the definition of fair value and the GIPS Valuation Principles.
注意条款中说的是fair value,不是cost也不是book value。
总结一下就是2000年以前的不需要追溯，211年后的必须要fair value对吗？