12. Which type of erosion forms limestone caves? A. wind erosion
B. stream erosjon
C. groundwater erosion

c. groundwater erosion

before it leaves the nucleus of a eukaryotic cell, mrna is altered in the following ways: - a cap is added to the 5' end of the mrna molecule; - a poly a tail is added to the 3' end; - introns are removed and exons are spliced together.

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.