"kubek" is a masculine noun so in Accusative (and actually also in Nominative) you use "ten".
"tę" is used with feminine nouns in Accustaive. For example:
Moja siostra lubi tę książkę (ta książka [Nominative] -> tę książkę [Accusative])
What means "My sister likes this book"
Is there no difference in Polish between a cup and a mug? Usually in English a cup is something your granny uses (along with a saucer) and a mug is something a builder (and the rest of us) use.
cup can be also "filiżanka"
and also puchar (for the champions etc)
I reccomend google image :)
It won't accept "that cup." I do not understand why it randomly does not accept "that" for "to" et al. Does anyone else know why? Or is this a programming mistake?
At the beginning of the course it only accepted "this" as translation of ten/ta/to, now course contributors try to add "that" to all sentences, but they missed some. Please report when you encounter one.