Which of the following statements about mutations is correct?
a. mutations always lead to genetic disease.
b. spontaneous mutations occur as a result of exposure to a mutagen.
c. mutations are alterations in normal dna sequence.
d. mutations are always inherited

The statement that is correct is C. Mutations are alterations in normal DNA sequence.

Explanation:

Mutations can be described as any changes in the sequence of the DNA. These changes might occur during the time of replication due to any error or it might be caused due to chemical or environmental factors. Hence, option C best describes the mutations.

Other options are incorrect like option A is incorrect because not all mutations lead to genetic diseases.  Option D is incorrect because mutations are not always inherited, they are caused due to changes in the DNA.

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.