I only see 3 excerpts.....those I can see would be as follows:
1) Society and class
2) humankind and nature
3) evolution
Don't know why the other 2 excerpts don't show up (for me)
Answer:
When Simon comes back tonight he will cook dinner.
Explanation:
Grammar
In <span> British English it </span>means<span> the exact opposite</span>
The importance of using a variety of sentence structures is to change up your writing. To make the reader engaged in what you have to say. If your sentence structure is weak and does not vary the reader might get bored. It also better shows your topic.
hope this helps! have a good day!