Hi there!
The correct answer is letter A) They elect members of the Parliament.
Argumentation:
Australia's Government rules by a federal parliamentary constitutional monarchy, which exercises its authority through a Constitution.
According to the constitutional structure, the Queen designates a General Governer for him to represent her (executive branch), and the General Governor appoints a Prime Minister (legislative branch) to represent the Parliament Representatives and Senate, and then there are the federal courts (judicial branch).
The Federal Parliament of Australia has two chambers: the Senate and the Representatives, which both are elected by the Australian citizens at federal elections.