Which widget allows you to select one alternative from a drop-down list?

The Combo Box Widget is designed specifically to allow users to select one alternative from a drop-down list, making it an ideal choice for scenarios where a single selection from a predefined set of options is necessary. It combines the functionality of a text box and a drop-down list, providing users with an easy interface to either select an option or input their own if needed.

This widget enhances user experience by saving space on the interface while still offering a clear method for selection. The nature of the Combo Box Widget also allows for a more manageable way to display numerous options without overwhelming the user.

In contrast, the Container Widget is primarily used to organize and group other widgets rather than to facilitate selection. The If Widget is a conditional logic tool that helps in flow control within applications, but it does not provide any selection capabilities. The Check Box Widget, on the other hand, enables multiple selections and is not limited to a single choice, which does not fit the requirement of selecting one alternative. Thus, the Combo Box is the optimal choice for this specific user interaction scenario.