**Coniferous trees** are a type of trees that have cones, needle-like leaves, and are typically evergreen. They are well adapted to cold climates, where they can withstand extreme temperatures and harsh conditions. These trees are commonly found in high-altitude regions, such as mountains and higher latitudes.

**Altitude ranges for coniferous trees**:
The correct answer to the given question is option 'A', which states that coniferous trees are found at an altitude of 1500 m - 3000 m. Let's understand why this is the correct answer:

1. **Altitude and climate**: Coniferous trees prefer colder climates, and as altitude increases, the temperature usually decreases. The higher the altitude, the colder the climate becomes. Coniferous trees are adapted to survive in low temperatures and can tolerate freezing conditions. Therefore, they are commonly found at higher altitudes where the climate is colder.

2. **Tree line**: The tree line is the elevation limit above which trees cannot grow due to harsh environmental conditions. As altitude increases, the tree line descends. The tree line is influenced by factors such as temperature, wind, and snow cover. Coniferous trees are often found near or above the tree line, as they are able to withstand the harsh conditions present at higher altitudes.

3. **Adaptations**: Coniferous trees have several adaptations that enable them to thrive in high-altitude environments. For example, their needle-like leaves help to reduce water loss and prevent snow accumulation. Their cone-shaped structure helps to shed snow and distribute weight evenly. These adaptations allow coniferous trees to survive in the cold and snowy conditions found at higher altitudes.

4. **Examples**: Some examples of coniferous trees commonly found at high altitudes include pine, spruce, fir, and cedar trees. These trees are often seen in mountainous regions, such as the Himalayas, the Rocky Mountains, and the Alps.

In conclusion, coniferous trees are found at altitudes ranging from 1500 m to 3000 m. These trees are well adapted to withstand the cold and harsh conditions present at higher altitudes, and their presence is often seen near or above the tree line.