You've moved the sentence, but now that you look at it, you're not happy with the change. Fortunately, you don't have to go through the entire cut-and-paste process again to move the sentence back to its original place. Instead, use Undo.
On the Quick Access Toolbar at the very top of the window, click the Undo button ( ). This will undo the last action you took, which in this case was pasting the sentence in the new location. Click the Undo button again to undo the previous action, which in this case was cutting the sentence from its original location. Or, to use another handy keyboard shortcut, press CTRL+Z twice to do the same thing.
Now your sentence is back in its original location.