Choices A and B. Somehow, when she reads this after the terminal opens up with it's shiny, delicious colors all over, it makes Terezi become reminded of a certain choice at a different place, and time. The consequences of them were much the same: Choose the right one or die.

However hard Terezi had searched, she only came upon two choices she could take, and that was either to stay her hand or to stab someone she once called her sister in the back. She had looked very far and quickly into the possibilities, but they all, for some confounded reason ended up only resulting in two outcomes. She didn't understand how that could be possible, but she hadn't the time to have think any further, or even discover the one possible outcome where she didn't have to do one of those two. One in which she could have still stopped Vriska, without her ending up dead on the floor, and one in which she could have every one of her friends live.

The moment she moved towards a choice, her finger hovered over the secondary of the choices. However, a flash of outcomes flashed before her eyes as if she had real sight again, only this time she didn't have to decide whether or not she had to kill anyone.

Paradox space has spoken.

Terezi chooses A.