What type of uv light is used during tanning beds and why is it so dangerous ?

It is an ultra violet light, same as the sun. If you spend a lot of time in the sun, you are more likely to get skin cancer, it's the same for tanning beds.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

the supermassive black hole is in the middle of the galaxy.