Teacher Student Jokes

Which tense is this?

teacher jokes in english
An old teacher questioned her class student, “Which tense is this, If I say, I am pretty beautiful. The student answered, “It is clearly past.”

Tree bark and dog bark

Teacher, “Sam! what is the outside of a tree called?”
Sam, “I do not know”
Teacher, “ Bark, Sam, bark”
Sam, “Bow, woof woof woof”  

Sleepy Head

Teacher, “Are you sleeping in my class?”
Student, “No, uh, a bug flew in my eye and I’m trying to suffocate it.”