This happened in one of my friend's bio classes - it's a good laugh for us but totally embarassing for this poor student.
The prof was talking about the reproductive system and for this particular lecture was focusing on the male reproductive system: so he's telling his class how there is a high content of glucose in the semen (or something along those lines) and one of the girls in the lecture puts up her hand and asks why does semen taste salty if there is such a high level of glucose in it
. Now let me tell you 2nd bio classes at UBC aren't small - about 300-400 are in these lectures.
When I first heard this story I nearly died laughing - oh that poor girl.