Final answer:
Sentence B, which states that evidence shows productivity improvements with four-day work weeks, makes a clear logos appeal by using factual evidence to support an argument.
Step-by-step explanation:
The sentence that most clearly makes a logos appeal is "B. Evidence shows that four-day work weeks improve productivity." This sentence directly references data and evidence, which are key aspects of a logos appeal, aiming to persuade through logical reasoning and factual information. The use of facts as evidence is a typical logos strategy, providing a rational argument supported by evidence to appeal to an audience's intellect and rational thought processes.