Give two functions of pericardium embrane

Understanding the Pericardium (Pericardial Sac) Your heart is surrounded by a double-layered membrane, called the pericardium or pericardial sac. This membrane keeps your heart in place in your chest cavity, restricts the expansion of your heart when your blood volume increases, and helps to protect your heart

The pericardium acts as mechanical protection for the heart and big vessels, and a lubrication to reduce friction between the heart and the surrounding structures. A very important role in all aspects of pericardial functions is played by mesothelial cells.

the index of refraction of the second medium is higher. i just took the test trust me !

instead of copying and pasting things off of tests or work done on computer which im sure you did, try and read over the question carefully