The correct answer is option 'D' - Tab stop.

Explanation:
When working with text in Microsoft Word, we often need to align the text in a specific way on the page. This is where the concept of a tab stop comes in. A tab stop is a position we set for placing and aligning text on a page.

Setting a tab stop allows us to control the horizontal placement of text in a document. By default, Word uses a left-aligned tab stop, which means that text starts at the left margin and extends to the right. However, we can change the tab stop to align the text differently.

To set a tab stop, we can follow these steps:

1. Open Microsoft Word and open the document where we want to set the tab stop.
2. Select the paragraph or text where we want to set the tab stop. This can be done by clicking and dragging the mouse cursor over the desired text.
3. On the Formatting toolbar, locate the "Tab stop" button. It usually looks like a small square with an arrow pointing to the right.
4. Click on the "Tab stop" button. A dialog box will appear, allowing us to set the tab stop position and alignment.
5. In the dialog box, choose the desired tab stop position from the options provided. We can enter a specific measurement or choose from the predefined options, such as left, center, right, or decimal.
6. Once we have selected the tab stop position, click the "Set" button to apply it to the selected text or paragraph.
7. We can repeat these steps to set multiple tab stops in a document if needed.

By setting tab stops, we can create columns of text, align text at specific positions, or create visually appealing layouts. Tab stops are a powerful tool in Microsoft Word for controlling the placement and alignment of text on a page.