UK A-Levels Politics Practice Exam

A by-election is specifically held to fill a vacancy that arises in the House of Commons between general elections. This vacancy typically occurs when a sitting Member of Parliament (MP) resigns or passes away. By-elections allow for the democratic process to continue and ensure that constituents are represented in parliament without having to wait for the next general election.

In contrast, the other scenarios listed do not accurately define when a by-election occurs. Election results being contested relates more to disputes and legal challenges rather than filling a vacancy. Holding a by-election during a general election period is unnecessary since general elections cover all constituencies. Lastly, verifying election results in key constituencies involves different processes and is not a reason for convening a by-election. Therefore, the correct situation leading to a by-election is indeed when a sitting MP resigns or dies.