The correct answer is not provided in the question. Delimitation of the Lok Sabha constituencies refers to the process of redrawing the boundaries of these constituencies to ensure that the representation is fair and equitable. The delimitation exercise is carried out periodically to account for changes in population and other demographic factors. However, the provided options do not specify the exact year when the last delimitation of Lok Sabha constituencies was done. Therefore, it is not possible to determine the correct answer based on the information given. It is important to note that delimitation exercises typically happen at regular intervals, so the last delimitation would have occurred relatively recently.