Which of the following foods is considered high in sodium?

Pickles are considered high in sodium primarily because they are preserved in a saline solution or brine, which is used to enhance flavor and extend shelf life. This preservation method involves soaking cucumbers in a solution that typically contains a significant amount of salt, leading to a higher sodium content in the finished product.

In contrast, apples, avocados, and corn are naturally low in sodium. They do not typically contain added salts and are often included in diets for their nutritional benefits without the concern of high sodium levels. This characteristic makes pickles a noticeable exception among the choices listed.