Why are zebra mussels able to spread so quickly in the United States? a. They are weaker competitors than the local mussels.
b. They grow logistically.
C. They are more zebra mussels than there are resources.
d. There are no natural predators of the zebra mussel in the U. S.

Zebra mussels reached North America in the mid-1980s in the ballast water of a ship. They rapidly became established in the Great Lakes and the waters draining them. ... They are very efficient filter-feeders, which means that they filter small organisms and organic particles out of the water at very high rates.