The left aortic arch is found in 
 

The left aortic arch is found in all mammals.

All mammals have four chambered heart whose biggest artery is the aorta that is the primary artery supplying blood from heart to the body organs. The left aortic arch connects the ascending and descending aorta. It is the segment of the aorta that helps in the distribution of blood to the upper parts of the body like the head. All vertebrates have left aortic arches and all mammals are vertebrates. 

Hence the correct answer is option A.