Which of the Following Has Not Been a Significant Issue

Which of the following has not been a significant issue in the creation of genetically modified (GM) organisms?

A) the fact that some plants carrying genes from other species might represent a threat to the environment
B) the fact that GM organisms cannot be modified to prevent them from reproducing once they pass beyond the experimental stage
C) the fact that the protein products of transplanted genes might lead to allergic reactions
D) the fact that rogue microbes might transfer dangerous genes into other organisms