Final answer:
The alcohol standard solution's ethanol concentration for legal blood alcohol levels is typically 0.08%. For other applications, the desired concentration may vary. (option b)
Step-by-step explanation:
The alcohol standard solution must adhere to different ethanol concentration ratios depending on the context. For legal blood alcohol levels, most states in the U.S. consider 0.08% by volume as the limit for being legally intoxicated. However, when discussing solutions in a laboratory or industrial setting, the desired concentration will depend on the specific application and can range from very dilute to very concentrated solutions, like the 75% mass ethanol solution or the 45% v/v solution presented in the given examples.
Hence, the answer is option b