In a classroom

This is your last Biology lesson for today. Despite that Ms. K was a good teacher, you never do any effort to study for her classes, so you never get a B. But the last weeks, you get worried about not getting to the college you want to. You tried the other subjects where you have best chances to get a B at least, but you don't succeed. So, Biology is your last option. You go to talk to Ms. K to improve your grades.

"I really want to help you, Mark, but your exams aren't even nearly to a B to let me remark the qualification."
"Please, Mr. K, I really need the B"

After thinking about it once more, Ms. K decides to give you a chance: "If you come after class, and help me with some work I have to do, I can give you extra credits, and in that way, you could reach the B."

You thanks her and return after class. You knock on the door, and Ms. K opens. You entered in the room and you see three female students sitting and waiting to start the class. You didn't know them, they're for another course. Ms. K presents you to the girls:

"Girls, he's Mark, and he will help us today for this class. Today we will learn male and female anatomy and reproductive organs. We will start with male anatomy and reproductive organs."

After saying that, Ms. K talk to you: "If you want the credits, you will do as exactly as I told you. Let me told you that if you don't want to do this, you can quit, but I will not give you the credits to reach the B. You understand?"

You nodded.

"Well, it's time to start the class. Mark, if you make us the favor, strip naked."

You are surprised at the odd order, and do not know if you really want all those girls see you naked. But you really need the credits.