C) parliamentary
The two main democratic forms of governing are parliamentarism and presidentialism.
In presidentialism the population choose the president through the vote, as it happens in the USA. In parliamentarian societies, the population votes to choose parliament and parliament chooses the prime minister, who acts as head of state.
Most democracies in Europe adopt the parliamentary system. Germany, Italy, Spain, England, among others, are parliamentarians. The main exception is France, whose regime is presidential.