How would you style all <p> tags with a red color using CSS?

To style all <p> tags with a red color using CSS, the appropriate declaration is to use the color property set to red. This is because the color property in CSS is specifically designed to define the color of the text within an element. When you write p { color: red; }, it effectively applies the red color to the text content of every paragraph element on the page.

Using other properties, such as text-color, would not work because text-color is not a valid CSS property. Additionally, choosing blue or green as the color would apply different colors than specified in the question, which is specifically asking for red. Thus, option B is the correct choice as it precisely meets the requirement of styling all <p> tags with the desired color.