Which of the following is an ad that opens automatically and does not disappear until the user clicks on it?

The correct answer is that a pop-up ad is designed to open automatically and remains visible on the screen until the user interacts with it, typically by clicking on it to close it or dismiss it. Pop-up ads are often used to promote products, services, or special offers and can appear in a new browser window or tab, capturing the user's attention directly.

This format can be particularly intrusive, as it disrupts the user's experience by overlaying content that they are currently viewing. Users generally find these ads annoying, leading to the significance of pop-up blockers in modern web browsers that aim to enhance user experience by preventing such interruptions.

In contrast, banner ads are typically static or animated graphics displayed on the top or bottom of a webpage, and they do not require user interaction to dismiss. Controlled ads might refer to advertisements that are regulated in some fashion but do not inherently imply an automatic opening mechanism. Portal ads usually refer to advertisements placed on internet portals or homepages, which also do not automatically open. Understanding these distinctions highlights the unique nature of pop-up ads in online advertising.