问题如下：
The product is a component of a price index based on a fixed basket of goods. If the product is substituted by other goods that have a lower price, the inflation rate calculated based on this index is most likely to:
选项：
A.understate the actual cost of living.
B.overstate the actual cost of living.
C.match the actual cost of living closely.
解释：
B is correct.
Upward biases such as the substitution bias will overstate the actual cost of living.
考点：Inflation Measurement
解析：因为当前部分商品可以用价格更低的商品进行替代，而计算时使用了固定的消费篮子，所以当前计算出的生活成本就被高估了。所以B选项正确。
能不能请另一位助理老师解释下，如果基期篮子不变，而当期用了更便宜的指数不应该是被低估了么？
