Identify the anatomical structure indicated by the blue arrow in the image below

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Options:
explanation: The image depicts an anterior view of the heart, which can be inferred from the position of the ascending aorta and the aortic arch travelling posteriorly which then continues as the descending aorta. The left anterior descending artery can be seen to the left side of the arrow (right side of the image).The arrow indicates the anterior border of the heart, which is directly in contact with the sternum anteriorly. The right border of the heart is formed by the right atrium, which forms the right pulmonary surface of the heart.
name: Anterior border of the heart – in contact with the right lung
label: b
answer: no
explanation: The image depicts an anterior view of the heart, which can be inferred from the position of the ascending aorta and the aortic arch travelling posteriorly to continue as the descending aorta. The left anterior descending artery can be seen to the left side of the arrow (right side of the image). The arrow indicates the anterior border of the heart, which is directly in contact with the sternum anteriorly.
name: Anterior border of the heart – in contact with sternum
label: a
answer: yes
explanation: The image depicts an anterior view of the heart, which can be inferred from the position of the ascending aorta and the aortic arch travelling posteriorly which then continues as the descending aorta. The left anterior descending artery can be seen to the left side of the arrow (right side of the image). The arrow indicates the anterior border of the heart, which is directly in contact with the sternum anteriorly. The posterior surface of the heart lies anterior to the oesophagus. This is an anterior view of the heart, so this is not the correct answer.
name: Posterior border of the heart – in contact with the oesophagus
label: d
answer: no
explanation: The image depicts an anterior view of the heart, which can be inferred from the position of the ascending aorta and the aortic arch travelling posteriorly which then continues as the descending aorta. The left anterior descending artery can be seen to the left side of the arrow (right side of the image).The arrow indicates the anterior border of the heart, which is directly in contact with the sternum anteriorly. The inferior border of the heart is, formed by the left and right ventricles and is termed the diaphragmatic surface of the heart, but it is not the area of the heart which the arrow points to.
name: Inferior border of the heart – in contact with the diaphragm
label: c
answer: no
explanation: The image depicts an anterior view of the heart, which can be inferred from the position of the ascending aorta and the aortic arch travelling posteriorly which continues as the descending aorta. The left anterior descending artery can be seen to the left side of the arrow (right side of the image).The arrow indicates the anterior border of the heart, which is directly in contact with the sternum anteriorly. The left border of the heart is formed by the left ventricle and part of the left atrium and forms the left diaphragmatic/left pulmonary surface. This arrow points to anterior surface of the heart, so this answer is not correct.
name: Left border of the heart – in contact with the left lung
label: e
answer: no

Correct answer: a