Which two statements describe disadvantages of genetic engineering?

a. a genetically engineered crop that has genes to resist pests can
be grown without chemical pesticides.

b. a genetically engineered crop that is resistant to insect pests
could also harm insects.

c. pollen from genetically engineered crops grown on farms can
spread to nearby wild plants.

d. crops can be genetically engineered to produce food more
efficiently than traditional crops can.