Question

вставить артикли a, an, the. ....Moscow is situated on...Moskva river and..London is situated on.....Thames

Answer 1

Moscow is situated on the river Moscow and London is situated on the Thames

Answer 2

Moscow is situated on the Moskva River and London is situated on the Thames.

Here, "the" is used before "Moskva River" because it refers to a specific river, while "the" is not used before "Thames" because it is assumed that the Thames is already known to the reader or listener. Also, no articles are used before "Moscow" or "London" because they are proper nouns.