All German Americans were required to join military armed forces. To those who hadn't signed up, were imprisoned.
But apparently, in many sources, it states that German-Americans in both Germany and US, were imprisoned. Sad truth :(
The primary causes were that Sparta feared of the growing power and influence of the Athenian Empire. The Peloponnesian war began after the Persian Wars ended in 449 BCE. This disagreement led to friction and eventually outright war. Additionally, Athens and its ambitions caused increasing instability in Greece.
The correct answer is D) generally harsh and abusive to workers