Which of the following activities is banned on the pier?

Choosing overhead casting as the correct answer reflects an understanding of safety and regulations that are often enforced on piers. Overhead casting can pose risks to other individuals nearby, as it involves swinging a fishing rod above one's head, which could inadvertently entangle other fishermen, pier visitors, or nearby structures. Safety regulations are typically introduced to ensure that all individuals on the pier can enjoy the space without the hazard of flying equipment or lines.

The other activities mentioned, such as swimming, walking, and shopping, may be regulated to some extent but do not have the same inherent risks associated with the potential for injury to others on the pier. Swimming is generally prohibited in many areas due to safety concerns regarding water conditions, while walking is typically encouraged for access and enjoyment, and shopping does not pose any physical risk to others. Therefore, understanding the specific reasons for banning overhead casting highlights the importance of safety and the types of regulations that are often put in place on piers.