Final answer:
The third step in overcoming a significant challenge like the COVID-19 pandemic is taking immediate actions, which applies the lessons learned from past experiences and reflection to mitigate the effects of the challenge.
Step-by-step explanation:
Reflecting on the challenges faced during the pandemic, the third step in overcoming a significant challenge, after listing past experiences and reflecting on lessons learned, should be c) Taking immediate actions. Immediate actions are essential to apply the gained insights and to mitigate the effects of the challenge at hand. For instance, during the COVID-19 pandemic, immediate actions such as social distancing, wearing masks, and initiating lockdowns were taken to control the spread of the virus. Actions need to be informed by what has been learned from past experiences and the reflection upon them, ensuring a strategic and effective response to the challenge.