"This is a house, Anna."
Translation:Это дом, Анна.
I must say that I actually feel your answer would be even more natural and correct from a Russian point of view, and older information (such as vocatives) tend to stand in the beginning of the sentence. I think that they've just translated from English, and ended up preserving its word order, and forgot adding the option.
As far as I can see the sentence was "This is a house, Anna" which is "Это дом, Анна". In English, at least, the order here can mean a significant difference in conversation.
Addressing someone by their forename after a statement is appropriate for talking to a child, perhaps, but it can sound condescending if addressing an adult.
Therefore the word order can be important to translate properly :)
i didn't care about learning russian before this because i never needed it. but now, a boy is joining our class tomorrow and he doesn't know any english so i am going to help him learn. if you read this comment, i dare you to pay it forward and do something nice for someone else. #payitforward
Again, old comment, I know, but (correct me if I'm wrong), it sounds like they're using the standard 'Moscow' dialect here, which means any unstressed 'o' sounds like an 'a'... making the two sound very similar.
I think -a is for feminine objects and -o is for neuter, generally speaking. (It's a long time since I studied Russian, so do double-check :)
Technically, o is not actually pronounced as "a" in Это - it is pronounced as a schwa. "Any written vowel can be a spoken schwa. A schwa is the 'uh' sound found in an unstressed syllable." Like the "o" in "button" or the "e" in "broken." The IPA symbol for schwa is /ǝ/. Google "schwa" for more information.