A solution is made by mixing 506 mL of water and 198 mL ethanol. What is the concentration of ethanol in units of volume/volume percent?
A. 39.1% (v/v) ethanol
B. 0.719% (v/v) ethanol
C. 0.391% (v/v) ethanol
D. 71.9% (v/v) ethanol
E. 28.1% (v/v) ethanol