Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. When snail or clam shells are left behind, they must be empty in order to remain durable and resist dissolution. B. Although snail and clam shells are durable and resist dissolving, over time they slowly begin to change. C. Although the soft parts of snails or clams dissolve quickly, their hard shells resist dissolution for a long time. D. Empty snail or clam shells that are strong enough not to dissolve may stay in their original state for a long time.