Answer:
Option B, A decrease in crop diversity.
Step-by-step explanation:
The genetic diversity will decrease because genetically modified crop with improvised trait will be a dominant species among all and hence in long run it will overrun all other species of crop which get affected by weed killers. Genetic material of genetically modified crops (GM) will subside the expression of any other genetic trait, thereby limiting the variation in the offspring in coming generation.
Hence, option B is correct