What voting system is used for Scottish Parliament elections?

The Additional Member System is the correct answer because this voting system is specifically designed for Scottish Parliament elections. It combines elements of both First Past the Post and Proportional Representation to ensure a more equitable representation of parties in the Parliament.

In practical terms, voters have two votes: one for a candidate in their local constituency and another for a political party on a regional list. This system aims to compensate for the disproportionate outcomes that can occur in single-member constituency elections, allowing smaller parties a better chance of being represented in the Parliament. The Additional Member System thus helps to create a Parliament that more accurately reflects the voting preferences of the population as a whole, making it a key feature of Scotland's democratic process.

Other voting systems mentioned do not apply to Scottish Parliament elections; First Past the Post is used for UK general elections, Proportional Representation is a broader category that does not refer specifically to the system in use in Scotland, and the Single Transferable Vote is used in various local elections and some other bodies, but not for the Scottish Parliament itself.