Answer: a. Biomes . . . ecosystems
Step-by-step explanation:
A biome is the region which includes the communities of living beings such as plants and animals. These are found in the range of the continents. The organisms living in a particular biome shows the characteristics typical to the biome and adaptations specific to the biome. Biomes becomes different on the basis of the physical climatic conditions specific to them.
The ecosystem is the communities of the species found in the biome. There are many ecosystems in the single biome.