Final answer:
Genetically modified crops were introduced because a crop failure can have a widespread global effect.
Step-by-step explanation:
The evidence that explains why genetically modified crops were introduced is option D) Today, a crop failure can have a widespread global effect.
Genetically modified crops (GM crops) have been developed to provide various benefits to farmers and the environment. By genetically modifying crops, scientists have been able to create crops that are resistant to pests, diseases, and harsh environmental conditions, such as drought and salinity. This ensures a higher crop yield and reduces the risk of crop failure, which could have a significant impact on food production on a global scale.