Final answer:
To align the date at a 4-inch left tab stop in a word processing document, you should press the Tab key. This will move the cursor to the tab stop, allowing you to then type the date aligned at that point.
Step-by-step explanation:
To align the date at a new left tab stop set at 4 inches in a word processing document, you would generally use the tab key. After setting the tab stop, you simply position the cursor where you want to insert the date, and then press the Tab key on your keyboard. The cursor will move to the position of the left tab stop that you have set, at this case at the 4-inch mark on the ruler. Once the cursor is in the right position, you can type the date, and it will align perfectly at the 4-inch tab stop.
The correct answer to the question is (a) Tab. The other options provided (Ctrl + Tab, Shift + Tab, and Alt + Tab) do not serve the purpose of aligning text at a set tab stop in most word processors.