I believe the correct answer is: C. by chronological order.
Chronological order represents the successive organization of statements, actions or facts, which means that they are arranged following one after another in time.
This passage of the cause-and-effect essay is organized in chronological order. The indications to that are the time references as “day”, “night”, and “years” which represent chronological cycle. Apart from that, the indications are also “then” and “now” which put the cause and effects one after another in time.