Final answer:
A stronger U.S. dollar against the euro benefits U.S. exporters the most.
Step-by-step explanation:
A stronger U.S. dollar against the euro means that it takes fewer dollars to buy one euro. In this case, U.S. exporters (option a) would be most likely to benefit. When the U.S. dollar is stronger, it makes American goods cheaper for European buyers since they can purchase more goods for the same amount of euros. This can lead to an increase in demand for U.S. exports and potentially higher profits for American exporters.