Misc: what measures walking distance?

Questions

Who succeeded Caligula as Roman Emperor?

Who is the subject of Anouilh's play L'Alouette ( The Lark )?

Which group had a British top five hit in the 1960s with Monday, Monday?

Which country's national flag consists of five-pointed yellow stars, one large and four smaller, in the top left corner on a red field?

From which country are the European Space Agency Ariane rockets launched?