A two-asset portfolio's risk and return are provided in the following table.

European Bond Weight	U.S. Stock Weight	Portfolio Standard Deviation	Portfolio Rate of Return
100%	0%	5%	4%
80%	20%	4%	5%
60%	40%	3%	6%
40%	60%	4%	7%
20%	80%	5%	8%
0%	100%	6%	9%

For an investor who considers only these two classes of assets and is willing to take risk up to a standard deviation of 4%, what is the optimal portfolio combination?

• A. 0% bond and 100% stock

• B. 40% bond and 60% stock

• C. 100% bond and 0% stock

• D. 60% bond and 40% stock