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

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Options:
explanation: This image shows a view of the inferior side of the diaphragm from within the abdominal cavity below it (the abdominal organs have been removed in this dissection). The arrow indicates the part of the diaphragm attached to the posterior wall of the abdominal cavity (it originates posteriorly from the lumbar vertebrae and associated lateral and medial arcuate ligaments). The base of the left lung lies superior to the left diaphragm, within the thoracic cavity. In addition, the parenchyma at the base of the lungs has a different appearance – more spongey – compared to that of the diaphragm, which is more muscular and thinner.
name: Base of left lung
label: b
answer: no
explanation: This image shows a view of the inferior side of the diaphragm from within the abdominal cavity below it (the abdominal organs have been removed in this dissection). The arrow indicates the part of the diaphragm attached to the posterior wall of the abdominal cavity (it originates posteriorly from the lumbar vertebrae and associated lateral and medial arcuate ligaments). The pericardium is a fibrous layer of tissue surrounding the heart, located within the middle mediastinum. It is not attached to the posterior wall of the thoracic or abdominal cavities as the structure indicated by the arrow in the image.
name: Pericardium
label: e
answer: no
explanation: This image shows a view of the inferior side of the diaphragm from within the abdominal cavity below it (the abdominal organs have been removed in this dissection). The arrow indicates the part of the diaphragm attached to the posterior wall of the abdominal cavity (it originates posteriorly from the lumbar vertebrae and associated lateral and medial arcuate ligaments).
name: Left side of the diaphragm
label: a
answer: yes
explanation: This image shows a view of the inferior side of the diaphragm from within the abdominal cavity below it (the abdominal organs have been removed in this dissection). The arrow indicates the part of the diaphragm attached to the posterior wall of the abdominal cavity (it originates posteriorly from the lumbar vertebrae and associated lateral and medial arcuate ligaments). The left pleural membrane surrounds the left lung and it has two layers (the visceral pleura – attached to the lung parenchyma; and the parietal pleura – attached to the left thoracic cavity wall). The arrow points to a structure located lower in the abdominal cavity. In addition, the pleural membrane layers are much thinner and softer in appearance, compared to the diaphragm which is a muscular structure.
name: Left pleural membrane
label: d
answer: no
explanation: This image shows a view of the inferior side of the diaphragm from within the abdominal cavity below it (the abdominal organs have been removed in this dissection). The arrow indicates the part of the diaphragm attached to the posterior wall of the abdominal cavity (it originates posteriorly from the lumbar vertebrae and associated lateral and medial arcuate ligaments). The intercostal nerves are thin structures passing in between the ribs. They pass in between the posterior intercostal membrane and the parietal pleura of the lungs, within the thoracic cavity. This is a view of the abdominal cavity, so the intercostal nerves are not visible.
name: Intercostal nerve
label: c
answer: no

Correct answer: a