By strict definition It could be argued that there's only ONE star on the flag that has Five of Six points eminating from a central region.
I *w*o*n*d*e*r* how many people answer Twenty! http://dictionary.reference.com/search?r=8&q=s tar
Australia has 6 states and a territory,I have a picture of the Australian flag in front of me and it has 6 stars,the picture is about 4 years old,they may have included one for the territory since.If they are your alternatives then 7 has to be your answer. 7?