Answer:
He has been living in the States, but he still does not have a command over the English language
Explanation:
In this exercise, you have to select the correct option to complete the sentence given. In this case, the correct option is "a" because "has been living" implies that this person is still living in the States. The present perfect continuous is used when you want to talk about something that started and may not be concluded yet.
"Have been living" is not correct (although it's the same tense) because "he" it's not plural.
