"The crab is an animal."
Translation:Yengeç bir hayvandır.
Why did it accept "Yengeç hayvandır."? Is "bir" optional here? If so why is it not optional in "Ben genç bir baykuşum." ? Also, when is it "t" when is it "d" the first letter of the suffix? I just can't find any hint in the tips about how this harmony rule goes. it is not a 2 or 4 way harmony, it seems to be something more complicated.