If the Sharpe Ratio for Interest Arbitrage Situations Is Low

If the Sharpe ratio for interest arbitrage situations is low, how may this explain why traders shun available profits and why UIP may not hold?

A) The ratio of rewards to risk is below the threshold required for investors.
B) Investors know that in the long run, their returns will be close to zero.
C) Investors are extremely risk averse.
D) There are known limits to arbitrage profits.