What is the main difference observed in the circulatory system of $Aves$ and $Mammals$?

• A
  In $Aves$,the aortic arch curves to the left,while in $Mammals$,it curves to the right.
• B
  In $Aves$,the aortic arch curves to the right,while in $Mammals$,it curves to the left.
• C
  In $Aves$,the heart is $3$-chambered,while in $Mammals$,it is $4$-chambered.
• D
  In $Aves$,the blood is cold-blooded,while in $Mammals$,it is warm-blooded.