"The child writes and reads."
Translation:아이가 쓰고 읽어요.
You add -고 at the end of the verb stem to connect two sentences with "and". Here, it just happens to be that the sentences are very short containing only a verb. The subject is the same for both.
Your connecting particles would be used for nouns for instance...
My guess is because it's connecting verbs rather than objects but I'm not sure
가 represent that we are talking about something specifically, while 는 is define we are talking about fact. For example
이 치타가 느립나다 This cheeta is slow.
치타는 빨라요 Cheeta is/are fast.
Oh my God! I use 는 in a sentence, and it requires 가, I use -습니다 ending and it needs -어요 ending. This is so frustrating! Even though I am correct, it tells me I'm not. I have already reported it, Apr. 10 2018.