Explanation:

The statement that a metamorphic rock is a result of a transformation of a pre-existing rock is correct. Metamorphic rocks form from pre-existing rocks (either igneous, sedimentary, or other metamorphic rocks) that undergo changes in temperature, pressure, or mineral composition, leading to the formation of new rocks with different characteristics.

The statement that uplift and erosion are the two forces behind the formation of metamorphic rocks is not correct. Uplift and erosion are geological processes that can expose metamorphic rocks at the Earth's surface, but they are not the forces responsible for the actual formation of metamorphic rocks. Metamorphism occurs primarily due to changes in temperature and pressure within the Earth's crust.

So, only statement 1 is correct.