Question

if cardiac muscle cells are unable to repolarize, this would cause multiple choice cardiac output to increase. no harm. these cells can spontaneously depolarize anyway. the heart rate to decrease. it might cause cardiac arrest. an increased demand on mitochondria to produce more atp. tachycardia.

Explanation:

Repolarization is crucial for the normal electrical - activity cycle of cardiac muscle cells. If they can't repolarize, the normal rhythm of the heart is disrupted. The heart rate would likely decrease and could lead to cardiac arrest as the cells are unable to reset for the next contraction - relaxation cycle. Cardiac output would not increase as the heart's ability to pump effectively is impaired. It is not harmless as it disrupts the normal electrical activity. There is no increased demand on mitochondria for ATP production in relation to the inability to repolarize in this context, and tachycardia (fast heart rate) is not the result of an inability to repolarize but rather a different type of cardiac electrical disturbance.

Answer:

the heart rate to decrease. It might cause cardiac arrest.