The question above is intended to assess your reading and writing ability and for that reason, I cannot answer this question for you, but I will show you how to answer it.
First, you must read the text to which your question refers and understand the relevance and impact of each key year.
Next, you should choose the two key years that you had the greatest understanding.
You can write the answer as follows:
Briefly summarize each key year.
Show the importance of each, that is, show why they are relevant.
