In the context of your CV, you are explaining things that you did. Simple past (your third example) is best, because you are not attempting to place your statement in a time context with another statement. Look at these:
I was teaching my students when the fire alarm rang and we had to leave the building.
I had been teaching for five years by the time I turned 25.
I taught academic oral language for five years.
In the first example, teaching is an activity that was ongoing when another event occurred. In the second example, teaching is an activity that occurred for a specific time period in the past that ended before another event occurred. (These two are somewhat interchangeable. For a good explanation of the difference, see here and here.)
In the last example, teaching is an activity that occurred during some five-year period in the past. This is most likely what you want. If you wanted to use one of the other tenses, you'd need to compare teaching to other past events, and those events wouldn't be relevant in your CV.
Now, one other possibility is the present perfect:
I have taught academic oral language.
This is fairly common if you are describing past experience that you have now: I have taught academic oral language, I have sold vacuum cleaners, etc. If you are describing the present state of your past experience, this is typically the tense used.
The usage of past perfect continuous indicates that the classes were before the exam. Past continuous would indicate that the exam occurred in the middle of the classes that she missed.
Past perfect continuous is probably the intended meaning.
"Betty failed the final test because she had not been attending class."
Regarding your edit:
The use of a past continuous generally indicates that the -ing activity was happening both before and after the event. If it's a recurring event it doesn't have to happen at exactly the same time as the event. For example, if the class is every Monday and the exam is on a Wednesday, the exam would not be at exactly the same time as the class, but you can still use past continuous:
She was attending classes at the time of the exam
What makes past perfect continuous the most appropriate in this case is that it's a final exam, which suggests that all of the classes were before the exam.
Best Answer
In real life, both (1) and (4) are grammatically correct, as Peter Shor commented. Which one you choose depends on what you want to emphasize the present or the past respectively.
For the purpose of the exercise, since the active voice is a simple past tense, a straightforward conversion to the passive would yield (4), which I believe is meant to be the "correct" answer.