What is required for a constitution to be changed in Australia through a referendum?

• A simple majority of voters
• A double majority of voters
  Explanation:

  "A double majority of voters is required to change the Australian Constitution through a referendum. This means that the proposed change must be approved by a majority of voters nationwide and a majority of voters in at least four of the six states."
• Only a majority of voters in the capital cities
• A majority of politicians in parliament