The primary factor in decreasing an object's kinetic energy is to decrease its velocity, as this has a significant impact according to the kinetic energy formula. Reducing mass can also help, but decreasing speed is generally more practical. Therefore, the correct answer is C. Decrease the velocity .
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To decrease an object's kinetic energy, the most effective method is to decrease its velocity, as this has a direct and significant impact according to the kinetic energy formula. Reducing mass can help too, but is often impractical compared to reducing speed. Understanding these principles is crucial in physics. ;