What is a defining feature of a cumulative voting system?

In a cumulative voting system, a defining feature is indeed that voters can concentrate all their votes on one candidate. This system allows voters to allocate their votes in a way that can amplify the support for a preferred candidate, which is particularly useful in elections where there are multiple seats to fill. For instance, if a voter has three votes to cast, they could choose to give all three votes to a single candidate rather than spreading them across multiple candidates. This can help minority groups or less popular candidates have a better chance of being elected by consolidating their support, making the election process more representative of diverse interests.

The other options represent voting systems with different rules and limitations, such as restricting voters to a single vote for one candidate or requiring that multiple votes be cast across different candidates without the option to concentrate them on a preferred choice. These alternatives do not align with the flexible voting strategy inherent in cumulative voting, which aims to provide voters with more control over their electoral influence.