Translation:In the morning I drink coffee; in the evening I drink tea.
In English, it's incorrect to connect two complete sentences with a comma (,) but without a conjunction (and, or, but, although, etc.). It would be correct to use a semi-colon (;) in this sentence's translation, though.
Counterexample: Roses are red, violets are blue, sugar is sweet, and so are you.
That example works only because it is a list of complete sentences. The "and" at the end makes the list grammatical. If it said "Roses are red, violets are blue, sugar is sweet, so are you", it would not be correct. Between any two independent clauses (complete sentences), you need a semicolon, a period, or a conjunction. In this sentence, only a comma is used. Either a semicolon or a conjunction (such as "and") is necessary.
Indeed, this is where Ukrainian is different from English. Comma splices are perfectly correct in Ukrainian.
Interesting... I changed it to semicolon in the exercise, but it's still showing a comma :/
OK great, now me too :) A comma will be accepted as well, of course, in fact, no punctuation at all is accepted (this is done automatically on all Duolingo courses). But the displayed English sentence will have a semicolon from now on. Thanks for the comment!