According to what I have read from news “immigrants who have lived in the country as legal residents for four years and want to become citizens will be expected to score at least 60 percent in a test of 20 questions taken randomly from a pool of 200 questions, covering issues ranging from “Australian values” to history, sport and political institutions. The test also gauges whether applicants have a basic grasp of English.”

Source: Newsmax.com

In any case according to Wikipedia the Official Language of Australia is English.

“English is the national language,^[46] and is spoken and written in a distinct variety known as Australian English. According to the 2001 census, English is the only language spoken in the home for around 80% of the population. The next most common languages spoken at home are Chinese (2.1%), Italian (1.9%) and Greek (1.4%).”