The words "high altitudes, harsh climate, and few trees" describe which united states ecosystem? alpine deciduous forest desert grassland

The words "high altitudes, harsh climate, and few trees" describes A. Alpine ecosystems in the United States. B is incorrect because Deciduous forest ecosystems have many trees. While C and D can have harsh climates and few trees, deserts and grasslands in the US are at very low altitudes. A is the only correct answer because alpine (mountainous) regions are very high thereby resulting in harsh climates that do not allow for the growth of many trees.