Explanation:

- In 1972, the West Bengal Forest Department acknowledged its inability to restore certain types of forests in southwestern districts.

- Option 1: Palash - Palash is a flowering tree known for its vibrant red or orange flowers. It is native to the Indian subcontinent.

- Option 2: Sal - Sal (Shorea robusta) is a significant timber-yielding tree found predominantly in India and the neighboring regions. It forms dense forests.

- Option 3: Piyal - Piyal is less commonly referenced in wide-scale forest conservation contexts compared to others listed here.

- Option 4: Segun - Segun refers to teak wood, known for its durability and value.

The West Bengal initiative particularly pertains to the Sal forests, known to dominate the region's landscape historically.

Option 2: Sal is the correct answer.