Contact Form 7 shouldn’t need any introduction. It is one of the most popular contact form plugins around with millions of installs. With extensions such as Conditional Fields, you can do even more with your contact form. Simply put what you want hidden between the start and end tag, and the plugin takes care of the rest.
Once you have decided the items you want hidden by default, you should go to the Conditional Fields tab to create the rules. The plugin supports nested groups. Conditions can be coded as plain text, which may be a faster option for those of you who have already gotten a hang of this plugin.
You can download this plugin fro free.