Your network contains a server named Server1 that has Microsoft SharePoint Foundation 2010 installed.
Server1 contains a Web application named WebApp1.
You activate the Office Web Apps Feature on WebApp1.
When users open Microsoft Office Word documents from WebApp1, the documents open in Word.

You need to ensure that when users open Word documents from WebApp1, the documents open in a Web browser.

What should you do?

A.
Deactivate the OpenInClient feature.

B.
Run the Set-SPWebApplication cmdlet.

C.
Restart the SharePoint 2010 User Code Host service.

D.
Recycle the SharePoint Web Services Root application pool.

Explanation:
Configure the default open behavior for documents
In SharePoint, you can configure whether browser-enabled documents are opened in a client application or in the browser. By default, when Office Web Apps is installed, Office documents will open in the browser. You can override this setting using the SharePoint OpenInClient feature. The OpenInClient feature can be configured in Central Administration or by using the SPFeature cmdlet in Windows PowerShell.

How documents open in SharePoint varies depending on whether the OpenInClient feature is present, and either enabled or disabled:
* If the OpenInClient feature is not present and Office Web Apps is not installed, documents will open in the client application (SharePoint default).
* If the OpenInClient feature is not present, Office Web Apps is installed and Office Web Apps service applications are activated, documents will open in the browser (Office Web Apps default).
* If the OpenInClient Feature is present and enabled, and Office Web Apps service applications are activated, documents will open in the client application.
* If the OpenInClient Feature is present and disabled, and Office Web Apps service applications are activated, documents in will open in the browser.

Source: http://technet.microsoft.com/en-us/library/ee837425.aspx