Which one among the following mahajanapadas in ancient India was an oligarchy?

From among the following Mahajanapadas, identify the gana/sangha (oligarchy) :

Which was the first capital of ancient Mahajanapada Magadh?

Champa was the capital of which Mahajanapada?

Which one of the following dynasties was ruling over North India at the time of Alexander’s invasion?

Which one of the following rulers of Magadha was the contemporary of Alexander, the Great?