When inhaled, crystalline silica can cause scar tissue to form on what organs?
a. eyes
b. heart
c. lungs
d. sinuses?

Option C, Lungs

Explanation:

When silica dust is inhaled it causes silicosis which in severe cases is disabling. When Silica enters the lungs , scar tissues are formed which lead to difficulty in taking oxygen. This problem usually arises when crystalline silica is inhaled continuously for a period of 15 to 20 years. Its symptoms are not visible and thus can only be determined through chest X-Ray. However, after prolonged exposure lung dysfunctions causes breathing problem, fatigue, chest pain or  respiratory failure

Hence, option C is correct

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.