Final answer:
To stop stem cell differentiation during culture, specific growth factors and a suitable substrate are necessary. These provide the signals and environment to maintain the stem cells in their undifferentiated state.
Step-by-step explanation:
In the culturing of stem cells, it is essential to prevent differentiation to maintain their stem cell properties. The correct conditions necessary to stop differentiation are specific growth factors and a suitable substrate (C). Growth factors signal the cells to divide and not to differentiate while a suitable substrate provides a physical environment that supports the undifferentiated state. It's incorrect to use low or high levels of oxygen and radiation (options A and B) as those can actually damage cells or influence differentiation. Similarly, exposure to environmental stressors and minimal nutrients (D) would not prevent differentiation and might induce stress responses or cell death. The balance of microenvironmental factors such as oxygen concentration does matter - while stem cells don't require either low oxygen levels or high radiation, they do often require carefully controlled oxygen levels that ensure their viability and undifferentiated state.