Class 9 Homework-

A heart attack can best be described as:

a. a sudden, harmful contraction of the heart muscles.

b. an invasion of heart tissue by pathogens such as bacteria.

c. a death of cells in the heart brought about by blockage of a coronary artery.

d. a failure of the nervous system to bring about heart contractions.

e. a rapid, harmful expansion of blood volume supplied by the heart.




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