Explanation:

When working with HTML, we can use the `target` attribute to specify how a linked document should open when the user clicks on a link. The `target` attribute can take several values, including `_blank`, `_top`, `_parent`, and `framename`, among others.

Opening a Linked Document in Full Body:
To open a linked document in the full body of the browser window, we can use the `_top` value for the `target` attribute. When a link with `target="_top"` is clicked, the linked document will open in the full body of the browser window, replacing any frames or iframes that may be present.

Comparison of Options:
Let's compare the given options and see which one opens the linked document in the full body:

a) `_blank`: This value opens the linked document in a new browser window or tab, depending on the browser settings. It does not open the document in the full body of the current window.

b) `_top`: This value opens the linked document in the full body of the browser window, replacing any frames or iframes. Therefore, this is the correct option for opening the linked document in full body.

c) `_parent`: This value opens the linked document in the parent frame of the current frame, if any. It does not open the document in the full body of the window.

d) `framename`: This value opens the linked document in the specified frame, if a frame with the given name exists. It does not open the document in the full body of the window.

Conclusion:
Based on the comparison, the correct option for opening a linked document in the full body is `_top`. This option ensures that the linked document replaces any frames or iframes and opens in the complete browser window.