this won't execute the input one at a time (looped) running the workspace for each choice separately.It's just feeding it 3 features, which is not the same.
There is multiple ways of doing this, but I would try:
Create an attribute from the parameter.
Use the AttributeSplitter (space delimited) to generate a list from the chosen values (AB and EB and TT).
The use the ListExploder to get features per value in the list.
Feed these features to the mentioned transformers that you need to execute.