Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

A product is part of a price index based on a fixed consumption basket. If, over time, the product’s quality improves while its price stays constant, the measured inflation rate is most likely:
Option A:unaffected.
Option B:biased upward.
Option C:biased downward.

Answer: B