Translation:Apart from tea, what else do you want to drink?
'In addition to' does not mean the same as 'besides', so I am completely confused by this sentence. Does the Chinese sentence mean that they are giving you a cup of tea and asking if you want another drink as well, or are they taking the teapot away and offering a substitute? Can anyone shed more light?
In addition is acceptable due to 还 which carries the meaning of something (similar) else. That's not to say that this is the best, or a good, translation, only that it is no unacceptable.
The first scenario you mentioned is possible, on its own. The second would be, too, with a context, such as a waiter clearing out the tea things.
This exercise is confusing because the Chinese is using the verb "除", but the official English translation is using the preposition "besides". I'd say that the literal translation of "除了茶" is "tea excepted" or "tea excluded".
Unfortunately, neither are excepted in answers in combination with "what else would you like to drink?"
It seems like the person who writes the Questions and the person that writes the Tips aren't communicating and occasionally contradict each other.
Question With Accepted Answer: 除了茶，你还想喝什么？ Apart from tea, what else do you want to drink?
Tip: 除了茶，你还想喝什么？ In addition to tea, what else would you like to drink?
My Answer Marked Incorrect: 除了茶，你还想喝什么？ In addition to tea, what else do you want to drink?
As you can see, the only difference between my incorrect answer and the accepted answer is that I used "in addition to" instead of "apart from". My answer applies what was taught in the Tips section while the accepted answer does not. It's frustrating because I feel this lack of self-consistency defeats the purpose of the Tips section altogether. :(
These are not translations.
This course is teaching us Chinese through English. So the answer teaches us what does 除了mean; what does 还 mean (assuming you already know what does 你 mean, what does 想 mean, what does 什么 mean etc.)
Just to let you know, I've been following this learning path. Build on the knowledge gained from past modules. Focus on - what's new in this module? In this sentence?
Rather than treating every single sentence I encounter here as a translation exercise... My 2 cents.