Markup and Web Languages

onreadystatechange is a PROPERTY (event handler) of XMLHttpRequest, not a method. You assign a function to it: xhr.onreadystatechange = function() { ... }. It's called when the readyState changes, but you don't invoke it as a method like xhr.onreadystatechange().

The open method of the XMLHttpRequest object takes the HTTP method as its first argument, and 'POST' is a valid standard HTTP method alongside 'GET'. Therefore, POST requests can indeed be sent using this method by passing 'POST' as the first parameter followed by the target URL.

The onUnload event fires when a document is unloaded from the browser window. This occurs in three scenarios: when the browser window closes, when the page reloads (including refresh), and when the user navigates away from the page (clicking links, back/forward buttons). Therefore, all listed conditions are correct.

innerHTML is a property, not a method. The correct syntax is document.getElementById('trial').innerHTML = 'value' without parentheses. Adding () as if calling a function causes a JavaScript error.

In the DOM Level 1 specification, innerHTML, innerText, outerHTML, and outerText are properties of Element objects. They are accessed and assigned like obj.propertyName, not called as methods with parentheses.

HTML elements like Form, Select, and Textarea do NOT inherit from Element in the DOM hierarchy. While they are DOM nodes, they inherit from specific interfaces (HTMLFormElement, HTMLSelectElement, etc.) that may or may not extend Element depending on DOM specification.

Although the open method of XMLHttpRequest is used to initialize the request and specify the HTTP verb (such as POST or GET), the request is not actually transmitted to the server until the send method is invoked. Therefore, the statement is false.

Web Parts in SharePoint use the .dwp (Web Part Package) file extension. These XML files define web part properties and configuration. The .dwp format was used in SharePoint 2003 and 2007, though later versions moved to .webpart files. Option B is correct among the given choices.

WSP (SharePoint Solution Package) files are deployment packages that can contain features, site definitions, list templates, web parts, assemblies, and other SharePoint artifacts. They're the standard unit for deploying custom SharePoint components. Option D correctly indicates WSP files are versatile containers for multiple solution types.

Web user controls in ASP.NET use the .ascx file extension to distinguish them from regular .aspx pages. The 'x' in ascx stands for 'extended' or 'user control.' Asmx is for web services, and Aucx is not a valid ASP.NET file extension.

To register a user control in an ASP.NET page, you use the @Register directive with the Source attribute (pointing to the .ascx file) and TagPrefix attribute. The TagName is optional in some contexts but Source and TagPrefix are the essential required elements for proper registration.

There are three main types of XML parsers: SAX (Simple API for XML) - event-based push parser, DOM (Document Object Model) - tree-based parser, and StAX (Streaming API for XML) - pull parser. Some might also consider character-only parsers, but the three major programming models are SAX, DOM, and StAX.