On Play Go at online-go.com! | OGS (excluding the mistake D), three options are listed: A, B, and C.
A and B are marked as ideal; C is marked as good and called slack.
This makes me consider two questions.
Isn’t it the case that Black can’t force White into any result inferior to those White can achieve with A and B?
If the only distinction of C from A and B is that Black can choose whether to tranpose to an A result or a B result, is that really suffiicent to mark C as non-ideal and call it slack?