Cameron was given the following series of observations. Which represents a theory?

When water freezes, it . contracts expands

Match each description to the appropriate biome. tropical savanna desert tropical rain forest taiga tundra has sparse vegetation and very cold temperatures located near the equator and contains trees that form dense canopy layers is very hot and dry, and has plants that need little water has cold winters, heavy snowfall and is dominated by conifers has warm temperatures and is dominated by grasses

What substance acts to prevent sudden ph changes in bodily fluids?