The correct answer is option 1, Diet. The Parliament of Japan is commonly referred to as the Diet. The Diet of Japan is the supreme legislative body and consists of two houses - the House of Representatives and the House of Councillors. The term "Diet" is derived from the German word "Diät", which means assembly or meeting. It was introduced in the late 19th century during the Meiji period when Japan was modernizing its political system. The Diet is responsible for making laws, approving the national budget, and overseeing the government. It plays a crucial role in the democratic governance of Japan. Therefore, option 1, Diet, is the correct answer.