Final answer:
Mobile habits (D) are the strategy not used to avoid desiccation in the intertidal zone, as the other options directly contribute to moisture retention.
Step-by-step explanation:
The strategy not used to avoid desiccation in the intertidal zone is mobile habits (D). Organisms living in the intertidal zone employ various strategies to cope with the drying effects of exposure to the air during low tide. These include burrowing into the substrate to maintain moisture (A), secreting mucus to create a barrier against water loss (B), and using a shell or outer covering as a physical barrier to retain water (C). Mobile habits, in this context, refer to the ability to move from one place to another and are not specifically a strategy used to prevent desiccation.