The following comments and questions were actually asked in college/university classrooms. How these people made it that far, I'll never know.
1. "If China is ahead of us by like a day, why didn't they warn us about 9/11?"
2. Prof: "No calculator is allowed on the test" Student: What if I use the calculator app on my phone?
3. This was a senior level college course and this guy was going to be our student speaker at our commencement. He said: "Wait, if Osama was killed then who's running our country?"
4. During the second week of class: "Hey do you know what day the professor hands out the textbooks?" That poor fool had no idea how much money he was about to spend.
5. First year world history, we had already spent 4 lectures discussing the Crusades.
Student 1: "So did the crusades have anything to do with religion?"
Student 2: "No, because the pope wasn't invented yet."
Nobody corrected them.
6. I was in an American History course and we were discussing the 1930's (and had been for a number of classes) when a girl who sat up front, who always arrived early and took very eager notes, raised her hand and asked "Wait, what's an F.D.R.?"
7. "I just don't think the cloud is safe. What if the weather is bad and you can't access your data?"
8. Teacher: "What was the name of the Indian that helped guide Lewis and Clark?" Student: "Sohcahtoa."
9. In a big lecture hall sociology class we were learning about social mores. A student asked, "is that what the song is about?"
Prof: "what song?"
Student: "When the moon hits your eye like a big pizza pie, that's a more?"
Entire class: stunned silence at the stupidity.
Then the prof does the kid the biggest solid I've ever seen by saying: "very funny."
But the student wouldn't drop it and says he wasn't joking!
Prof: "trust me, you were joking."
Class: uproarious laughter. - Source
10. During a discussion about reincarnation: "What if you got reincarnated as, like, a wasp, and you were like 'I don't like wasps!' and stung yourself?"
11. Venezuela is in Africa right?" and "Wait....Australia is a country and a continent?!?" Same girl asked these.
12. A girl was very upset while we were talking about black Europeans. She calmly told us that they prefer the term "African Americans." She could not wrap her head around why that was not correct.
13. "Why don't the terrorist countries have to follow the constitution?"
14. "And there was a hipp... a hipp...a funny-lookin' elephant." He was trying to find the word hippopotamus...
15. "The leader of North Korea looks like Psy. What's his name? Like Genghis Khan or something?"
16. About to write our final exam for a Calculus class.
Professor: You have 90 minutes for this exam.
Student: But you told us we have an hour and a half!
17. "Is longitude the one with the globe, or the one with the mountains?"
18. In junior year of college, I was with a class in an anatomy lab looking at very dead, very naked, and very obviously male body. We were going over the body and we got to the lower half, where the deceased's twig and berries were prominently on display. The dim bulb of our group seized on a moment of silence to point to the man's genitals and ask the professor, "...are those the ovaries?" - Source
19. Middle of an exam:
"Is this being graded?"
20. A student in my friend's veterinarian program wanted to know what would grow if you planted popcorn kernels outside.
21. "So 'cat' is the past tense of 'cut' right? Like, 'I cat myself with my knife.'"
22. "But doesn't the Sun revolve around the Earth?" This girl was in her third year of an Education degree
23. "So all 435 representatives live in one house, right?"
24. In a Geography course in my 3rd year of university, a friend of mine asked near the end of a lecture on the Greenhouse Effect), "Why wouldn't they just stop building greenhouses?!"
25."How do dogs in other countries function when their owners say things like 'pelota' instead of 'ball'? Like how do they know what a ball is when the owner talks Spanish? Sooo weird."
26. "Are cows counted in part of the population?"
A girl in my history class asked this last year, completely serious. Our teacher looked like he was in pain after hearing it.
27. Typical hippie chick on the first day: "Is this class going to cover non-western contributions to history?" The class was History of Western Civilization.
28. While discussing exchange rates in a third year economy course: "So, if the Euro's worth more than the dollar, couldn't I just like convert my dollars into Euros and convert them back so I could get more money?"
29. Professor: So who can tell me about Pearl Harbor?
Girl in the first row: Oh. my. god. I LOVE that movie.
Turns out she didn't know the movie was based on a real life attack on Hawaii.
30. "Sorry I'm late, would you mind starting over?"