it could be a bi male/straight guy or a bi female/lesbian who thinks she's hot, or it could be a picture of the person (thus a girl of any sexuality)... or it could be a girl a bi male/gay guy admires... so basically, it could be someone of any gender and sexuality yeah, this is why you shouldn't make assumptions based on stuff like that ^.^
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Open your eyes and look at everything or admit to partial blindness.