What gender should my main charecters be?

My charecter is currently a girl. But, I originally wanted to leave the gender ambiguous. Now, I want a solid answer. I made a poll of this, just ignore it. The charecters name is Bentley, and I don't know if the plot really applies to what their gender would be, so I'm not gonna explain it. But here are the options:
-Male
-Female
-Transgender (male into female)
-Transgender (female into male)
-Agender
-Bi-gender (being both male and female at the same time, or feeling more like one at one time, and the other at another. I personally identify as bi-gender.)
-Any other gender that I have not listed. Feel free to tell me then!
Also, keep in mind the definition of gender. Ones gender identity and their actual body are different. Gender is how you feel, and how you identify mentally.
So if Bentley we're to be a bigender, such as myself, they would not have male and female body parts, but instead a male and female mentality.
Thanks to anyone and everyone who helps! Much appreciated! Sorry for such a long description, but once again, thanks!