Hello. You did not ask the question to which this text refers, which makes it impossible for me to give you an answer. However, when searching the internet, I found a question that used that same text and asked what was the verb tense of the text and what was the meaning of the phrase ‘this green flooring’. If that's your case, I hope the answer below can help you.
The verb tense of the text in the first sentence is Simple Past. Since the verbs "had landed" have an action performed in the past and that has been completely completed. However, the second sentence presents the past tense Past Perfect Continuous, as it presents an action that happened in the past before another action happened, since we can see that the characters waved before starting to call out stridently.
The phrase "this green flooring" refers to the characters stepping on a floor with vegetation and therefore stepping on a "green flooring."
The right answer for the question that is being asked and shown above is that: "thermonuclear." The <span>idea that does Sagan stress through the use of parallelism is the word thermonuclear.</span>
Like the Phoenix, which rises from the ashes, they will rebuild their society from the destruction caused by the bombing and the damage caused by outlawing books.