In English, large, great rivers, such as Dnipro, Seine, Mississippi are always refereed to as "the" xyz river.
While I certainly agree about the spelling, I also don't understand the error of omission with regard to the word "the." In English it would be truly bizarre to refer to specific landmarks such as Statue of Liberty, Colorado River, etc. without using the definite article "the."
It is strange to be told I am incorrect in my native tongue when I know that it is - in fact - not incorrect.
I am just happy to have this Ukrainian course. And it is because of that feeling that I don't see any reason to get too upset about being marked "incorrect."
But it is a little discouraging when odd inconsistencies appear and tell me I am wrong and then - at other times - told I am right. The rule regarding the use of "the" in English is pretty standard though not necessarily universal. If the noun is a singular type of landmark (not just the general term "river, building, etc.) then the use of "the" is required. If it is general, that is it lacks a proper noun (river, city, etc.) then the indefinite article "a" is generally applied. Sheesh.