In my case "A bird flies" was shown as the correct answer ( I wrote Bird flies). I guess sometimes they are using "The" some times "A" and other times not using any article at all. Confusing !
You are absolutely right
Yes,you are absolutely right
if "A bird flies" then why not "pakshi urta huta hai"?
That's a construction you could use if you specifically wanted to emphasize the habitual nature of the activity. To make a general statement, the example given is sufficient.
I say that's wrong because it says "पक्षी उड़ता है" not "वो पक्षी उड़ता है", which shows a specific bird.... thus it's grammatically incorrect.