Consider the following statements about the Himalayan mountain system:

I. The Himalayas are not a single chain but consist of multiple parallel ranges with distinct characteristics.

II. The three main divisions are the Greater Himalayas (Himadri), Lesser Himalayas (Himachal), and Shiwalik ranges.

III. These ranges are separated by longitudinal valleys known as 'Duns' in the western Himalayas.

Which of the statements given above are correct?