Right. It shouldn't mark it wrong just because you didn't put "the". But here's the thing: In English, when you use a common noun, you do put an article before it, or it changes the meaning of the sentence. e.g. Peacock is a bird= "someon named Peacock" is a bird. A/the peacock is a bird= every peacock (understand to be an animal but not human) is a bird.
You better let this kind of mistakes because we are learning hindi not English grammar