creating a dimension table from multiple columns in a fact table

Good morning

i am trying to look at some survey data. I have a question that is multiple select answers. Each answer appears in a separate column in my table. (It is an external data source).
what i need to do is to merge them into one column, so i can say 10% prefer option a compared to 5% prefer option c, as it is multiple choice some people have selected more than one answer
Is there a way of doing this? or if not any suggestions as the best way to show this

Thank you