Basic Trope: A game seems to give you several route options, but there's really just one option.
Straight: At some time in Tropeland Chronicles, Princess Maria asks Tana if she wants to help her Find the Cure to a mysterious illness that's spreading across her kingdom. You are given a multiple-choice question and a Dialogue Tree. The four options are "Yes", "Of course I'll do it for you", "Sure", and "Anything for you, Your Highness"
There are 50 different options, all of which are affirmative.
You get a huge Dialogue Tree with ten choices the first time, each leading to ten new choices that each lead to ten new choices. No matter which of the 1000 combinations you end up choosing, you'll end up agreeing to help Maria.
Every single decision in the game is like this.
Downplayed: There are two options, "Yes, of course! After all, it's a duty to help those in need" and "Sigh. I guess I have to". The latter leads to Maria respecting Tana slightly less.
Tana adores Maria and wants to help her. The player gets more freedom when Tana's opinion is more unclear.
A spell forces Tana to accept any command given to her.
All the choices are refusals and offer different possible paths. You can even change your mind later.
The only option is "Yes", but after choosing it, you're free to do whatever you want.
Subverted: The visible options are all affirmative, but scrolling down reveals some negative responses.
Choosing a negative response leads to Maria asking again and again until you finally agree.
There are all kinds of responses, but Maria interprets everything as affirmative, even "No way I'm doing that. It's not my problem".
The player is allowed to write a response. Maria treats everything as affirmative, potentially leading to situations like this:
Tana: HELL NO! Screw you and your stupid kingdom! Maria: I knew a good girl like you would agree to help me out! We should be best friends forever!
Sometimes you get nothing but affirmative/negative responses, sometimes you get multiple responses, but choosing incorrectly leads to a Non-Standard Game Over, sometimes the NPCs will ask repetitively until you choose the right answer, sometimes you actually get a choice...
The visible options are all affirmative, but scrolling down reveals some negative responses. Choosing a negative response leads to Maria asking again and again... until you reach 13 refusals, after which she says "Fine! Just let everyone in my kingdom die slowly and painfully, you selfish bastard!" As Tana tries to leave the castle afterward, a guard tells her he won't let her leave before she has agreed to help Maria, but the guard is easily defeated. Then a witch curses Tana so that she can't leave the castle before she has made a Magically Binding Contract to help Maria... but it turns out that there's an alternative way to break it. However, by the time the curse is broken with the alternative method, the disease has spread all across the kingdom. If Tana tries to leave the castle through the kingdom, she'll get infected and die, and there's no other way to leave the castle.
The player is free to choose whether to help Maria.
In a cutscene, Tana agrees to help Maria. There's no choice, but no illusion of choice either.
"So, how can we railroad the player to help Maria?"
Making a CYOA is hard enough, dealing with people going Off the Rails is too much for the poor game designers.
Lampshaded: "Tana, I don't think you really have a choice there."
Invoked: One of Maria's servants curses Tana, forcing her to obey Maria's commands.
Exploited: Maria starts asking for more favours from Tana because she has to accept them.
Discussed: "Sometimes I wonder if I have free will or everything is pretermined. Was helping Maria my choice or was I fated to help her?"
Conversed: "Another game that only gives you an illusion of choice."
Plotted A Perfectly Good Waste: This is done to show that the narrator is actually a deity that loves to use his powers to control others. Said deity pretends to be benevolent at first, but his true nature gradually starts showing, and Tana has to fight him throughout the second half of the game.