Consider the following pairs : National Highway Cities connected 1. NH 4 : Chennai and Hyderabad 2. NH 6 : Mumbai and Kolkata 3. NH 15 : Ahmedabad and Jodhpur Which of the above pairs is/are correctly matched?

Let's analyze each pair concerning National Highways and the cities they connected, keeping in mind the numbering system changes over time:

1. NH 4 : Chennai and Hyderabad: Historically, National Highway 4 (NH 4) connected Mumbai and Chennai. Hyderabad was not on the primary route of NH 4. With the renumbering of National Highways in 2010, the old NH 4 was subsumed into other new National Highways, primarily NH 48. Therefore, this pair is incorrectly matched.

2. NH 6 : Mumbai and Kolkata: Historically, National Highway 6 (NH 6) connected Dhule (Maharashtra) to Kolkata (West Bengal) via Nagpur, Raipur, Sambalpur, and Kharagpur. While it connected towards Mumbai from Dhule and definitely reached Kolkata, it was not a direct Mumbai-Kolkata highway as much as a Dhule-Kolkata route that facilitated connections to Mumbai. Under the new numbering system, most of its alignment has been renumbered as NH 53. Therefore, this pair is incorrectly matched in its primary, direct sense.

3. NH 15 : Ahmedabad and Jodhpur: Historically, National Highway 15 (NH 15) ran from Pathankot (Punjab) to Samakhiali (Gujarat), passing through Rajasthan (including Jodhpur) and Gujarat. While Jodhpur was on NH 15, Ahmedabad was not directly connected by its main route. Under the new numbering system, parts of old NH 15 are now NH 62 and NH 68, among others. Therefore, this pair is incorrectly matched.

Given the historical and current contexts of National Highway numbering and their routes, none of the provided pairs are correctly matched.