All of the following are true of the zebra mussels found in the great lakes except:
a. zebra mussels are having are having a negative impact on the native population of mussels in the region.
b. they were unintentionally introduced to the great lakes by humans.
c. zebra mussels have caused a great deal of environmental damage to the area.
d. people of the great lake region are benefitting from the economic advantages of having zebra mussels in the region.