Political Bias in My Teaching?

I've long been curious about what students in my classes think about my political position. So, I finally decided to ask them. I added a bonus question for 1 point on top of the 100 points available for the final exam in my Energy Economics course. The question read:

Bonus question (1 point): 
This question relates to potential political bias in my presentation of the course material. Based on the content of the course, which political party do you think I voted for in the last Federal senate election?

a. Greens
b. Labor
c. Liberal
d. Liberal Democrats
e. Australian Sex Party
f. Christian Democratic Party

Actually, ten parties ran at the last election for the two available senate seats representing the ACT, but I thought it would be better to keep the list a little more manageable.

The distribution of answers was as follows:

Greens: 2
Labor: 5
Liberal: 5
Liberal Democrats: 5
Australian Sex Party: 0
Christian Democrats: 0

Assuming that everyone who picked Liberal Democrats knows what it is - a libertarian party - there is a perceived rightward bias. But there are a lot of foreign students who might assume it is a more centrist party. Or people might have assumed that if I listed a bunch of parties they hadn't heard of, one of those must be the right answer.

What would no bias look like? Maybe something more like Green 2, Labor 7, Liberal 7, Liberal Democrat 1 or 3,7,6,1, which is closer to the voting pattern. Or maybe even further to the left as most academics including economists in Australia probably vote for Labor, so that would be the default assumption unless they perceived a strong bias in my teaching?