Final answer:
Both Mark and Sarah are correct. Flush docks are commonly used in the U.S. and offer security and protection from the elements.
Step-by-step explanation:
Mark and Sarah are discussing docks in the U.S. Mark says that flush docks are the most commonly used today, while Sarah says that flush docks provide the most security and protection from the elements. In their discussion, both Mark and Sarah are correct.
Flush docks, which are level with the ground, are indeed the most commonly used type of docks in the U.S. They offer easy access and efficient loading and unloading of goods.
Additionally, flush docks do provide security and protection from the elements. They are built to be sturdy and are designed to prevent water from entering the dock area, thus protecting the goods and equipment from damage.