If there is a lack of oxygen in our muscle cells, pyruvate breaks in a different pathway. Glucose (a 6-carbon molecule) breaks into pyruvate (a 3-carbon molecule) and pyruvate is then converted to lactic acid (a 3-carbon molecule) along with the release of energy. The buildup of lactic acid in our muscles due to sudden activity can cause muscle cramps. Hence, the correct option is (c).