The correct answer is option 4: Deodar.

The Deodar is a species of vegetation found in the Himalayas at altitudes between 1800 to 2600 meters. Deodar, also known as Himalayan Cedar, is a large evergreen tree that is native to the western Himalayas. It is characterized by its silvery-blue leaves and dense, conical shape.

Option 1: Saal refers to the Shorea robusta tree, also known as the Sal tree, which is found in the lower regions of the Himalayas. It is not typically found at altitudes between 1800 to 2600 meters.

Option 2: Chir refers to the Pinus roxburghii tree, also known as the Chir pine, which is found in the western Himalayas. While it is found at higher altitudes than Saal, it is not specifically found between 1800 to 2600 meters.

Option 3: Spruce refers to several species of coniferous trees in the genus Picea. While Spruce trees are found in the Himalayas, their altitudinal range is typically higher than 2600 meters.

Therefore, the correct answer is option 4: Deodar