C is possible in this sentence.Hello!
At the meeting, even though he spoke well, he __________ persuade the other members.
A. was able to
D. was unable to
The key is D but I am wondering why C isn't chosen, please?
Thank srb62!C is possible in this sentence.
However, I think D has been chosen as the correct answer to help learning.
Sometimes couldn't/was unable to are interchangeable, but sometimes they are not.
I think the idea here is to make you focus on the idea of trying to achieve a goal, but in the end not achieving this goal.
I hope that makes sense, and I'd be interested to hear what others thought.