Proportional representation favours a:

Proportional representation is a system of voting that aims to ensure that political parties are represented in proportion to the number of votes they receive. In this system, parties are allocated seats based on the percentage of votes they receive in an election. This system favours a multi-party system, as it allows for smaller parties to have a chance of gaining representation in government. It is less likely to favour a two-party system or a one-party system, which tend to limit political diversity and representation. Therefore, the correct answer is: multi-party system.