Which of the following is a medical application of genetic engineering?

Pharmaceutical development is a crucial medical application of genetic engineering. Through genetic engineering, scientists can manipulate the genetic material of organisms to create medications and treatments. This includes the production of recombinant proteins, such as insulin for diabetes management, growth hormones, and monoclonal antibodies for cancer therapy. These genetically engineered proteins are often produced in bacteria, yeast, or mammalian cells, providing a more efficient and effective means of producing essential drugs compared to traditional methods.

In this context, while selective breeding of livestock and traditional vaccine preparation are important biological applications, they do not directly involve the precise modifications of genes for therapeutic purposes that define pharmaceutical development. Additionally, organic farming practices focus on cultivation techniques that minimize the use of synthetic fertilizers and pesticides, which aren't directly based on genetic engineering. This makes pharmaceutical development the most relevant choice among the options provided.