Specificity in CSS determines which style rule takes precedence when multiple rules target the same element.

The correct option is a) first-line. The ::first-line pseudo-element in CSS is used to style the first line of text within a block-level element, allowing for fine-tuned typography control.

The correct option is 1fr. The repeat() function in conjunction with 1fr will create three columns of equal width. auto would not ensure equal width. equal is not a valid value. 100px would fix the columns to a specific width, not making them equal.

On high-DPI displays, such as Retina screens, icon fonts may appear blurry due to pixel scaling. This is addressed by using font-smoothing techniques like antialiasing and ensuring that the font files are designed for high-resolution displays.

To ensure that each row accommodates the tallest item without stretching the shorter ones, set the grid-auto-rows property on the grid items using minmax with a specified minimum height. This allows the row to adjust based on the content's height while preventing excessive stretching.

CSS sprites combine multiple images into a single file, reducing the number of HTTP requests made by a browser to fetch individual images. This consolidation significantly improves page load performance, especially for websites with multiple small images. While it doesn't directly impact file size or server-side caching, it plays a crucial role in optimizing web page loading times.

The width property specifies the content width of an element. However, if you have set a width and include padding or borders, the total width of the element will be affected. Understanding the box model is crucial for accurately controlling the size of elements.

SASS Variables offer additional features like nesting, making the code more modular and maintainable. This can be an advantage over CSS Variables, which lack some of these advanced features.

The correct option is visibility-print. This CSS property is specifically used in print stylesheets to control the visibility of elements when the document is printed. The visibility-print property helps tailor the content for a better print layout.

In Styled Components, the extend method is used to create a new styled component based on an existing one, allowing for easy reuse and extension of styles.

Feature detection involves identifying and adapting to the specific capabilities of a browser, ensuring consistent performance across different browsers. It goes beyond identifying versions, focusing on handling capabilities to enhance cross-browser compatibility.

When creating a custom CSS gradient, the first color stop can be defined at the "beginning" position, allowing designers to customize the starting point of the gradient, influencing its overall appearance and visual impact.