Which of the following methods can effectively minimize stress in research animals?

Frequent handling of research animals is an effective method to minimize stress because it helps them become accustomed to human interaction and their environment. Regular, gentle handling can promote trust and reduce fear, making the animals more comfortable when they are being cared for or when they participate in research activities. This acclimatization can lead to a reduction in stress-related behaviors, allowing for better health and more reliable research results.

In contrast, keeping animals in isolation, using aversive methods, or limiting human contact can all contribute to increased stress levels. Isolation can lead to loneliness and anxiety, aversive methods can cause fear and distress, and decreased human interaction can prevent animals from becoming accustomed to their handlers or environments. Thus, frequent handling is beneficial in creating a more positive and less stressful experience for research animals.