How to change ASP.NET WebMethod's 'd' identifier in a JSON response, to a different name?

This works: through jQuery I'm using a jQuery.ajax(..) call to a page e.g. Default.aspx/GetStatus having a WebMethod attribute:

// Default.aspx
[WebMethod()]
static public bool GetStatus(long id)
{ //...

The JSON response contains the correct boolean value in the format { d: true }. However I don't understand the origin of the resulting "d" member name.

Where does the "d" identifier come from (how is it dec开发者_JAVA技巧ided) and how can I change its name?

---

What does .d in JSON mean?