Correct Answer:
A. Siwalik Range
The Sub-Himalayas are also widely known as the Siwalik Range (or Shivalik Hills). This range represents the southernmost and geologically youngest east-west mountain chain of the Himalayas. It is characterized by foothills and low mountains. The Margalla Hills are a part of the Siwalik Range near Islamabad. Pir Panjal is a range within the Lesser Himalayas, which is distinct from the Sub-Himalayas. Koh-e-Suleman (Sulaiman Mountains) is a separate mountain range located in western Pakistan, not part of the Himalayan system, making these options incorrect.