Batteries are hazardous primarily because they contain acid, especially in lead-acid varieties. This acid poses a significant risk of injury or damage during battery failure or mishandling. Therefore, the correct answer is that batteries contain acid (Option C).
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Batteries are considered hazardous primarily because they contain acid, particularly in lead-acid batteries. This acid can cause severe injuries if batteries are damaged. While other hazards exist, the presence of acid is the most significant concern. ;