Here's the context.
Scott said he had been studying Greek for more than five years. If he had been studying the language that long, I think he would have been able to interpret for us at the airport.
- The reason he wasn't able to interpret for us at the airport was that he hadn't been studying Greek for more thatthan five years.
- The reason he wasn't able to interpret for us at the airport was that he didn't study Greek for more thatthan five years.
- The reason he wasn't able to interpret for us at the airport was that he wasn't studying Greek for more thatthan five years.
I feel #1,2 are possible but, #3 sounds awkward. but still, I'm not sure how which one is different from others. Could you let me know the differences between them?