In the original Star Trek movies, why does Saavik go by "Mr."?

Question

She's a girl, so why do they all call her "Mr. Saavik"?

Answer 1

Because she was an officer.

Answer 2

Oh, you know those wild,crazy Vulcans! Have you ever heard of their mating ritual? YIKES!

Answer 3

Its just like calling a military officer Sir even if it's a woman.  Granted, these days some prefer Ma'am but many still go by sir.

Answer 4

In naval tradition (which the StarFleet rank structure is based on) all officers are called "sir" no matter what the gender.