Translation:Her mom drinks tea every day.
It appears unnatural not to have 都. (We can also use 也. The meaning is the same. ) I don't know exactly why. I think it is a matter of emphasis. Usually if there are more elements in the sentence, it becomes more likely that 都 can be skipped.
Her mother drinks tea everyday because she thinks it is healthy.
Her mother drinks tea, has plain congee, and does morning exercise everyday.
These appear natural to me with or without 都.
I agree it really puts you out with no explanation as to why. It sounds like she has more than one mother, due to the 都
I thought it meant that 'she and her mother both drink tea' as I could not see the what dou 都 is there for.
I would say it’s not absolutely necessary but it sounds more natural to me.
An explanation of the 都 here: https://resources.allsetlearning.com/chinese/grammar/Emphasizing_quantity_with_%22dou%22
when we have to translate the other way, the sentence with "dou" is marked wrong, I am not sure why
I wrote "Her mother drinks tea every day" and got a wrong answer. Is "mother" different from "mom"?
"Mother" is not different from "mom". Perhaps the system did not recognize the word, "mother". Not your fault.
With the audio exercise, there's no way to distinguish 他 from 她. I used the masculine (it's the only difference I had) and it didn't accept it, and there's no way to report it.
I reported it as a different error, because there's no way to say "My answer should have been accepted" on these exercises.
Given that this is a listening exercise, why isn't "他的妈妈每天都喝茶" also accepted? I am not aware of a way to determine somebody's gender when they are referred to in the third person in Mandarin, unless the subject's name is included.