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.

Tactical asset allocation is best described as:
Option A:attempts to exploit arbitrage possibilities among asset classes.
Option B:the decision to deliberately deviate from the policy portfolio.
Option C:selecting asset classes with the desired exposures to sources of systematic risk in an investment portfolio.

Answer: B