One way to vary the syntax of the text is to combine sentences since, in this way, your structures will be longer and more complex to follow. This could be done by means of links such as: however, in addition, therefore, etc. When using these words, you create semantic relations between the syntactic structures and make the reading process more difficult because, as I've I said, sentences become longer and therefore the reader has to keep more information in mind to follow the train of thought.
You could also vary the syntax by adding phrases or clauses. This option is similar to the previous one since it also refers to the complexity of the syntactic structures of the text.
This is speculation, so please get a second opinion.
I think it's c, because the adults, in this passage, are teaching children how to behave, and therefore a and b are ruled out. d could have possibly been one, but I think that it would not be, because the adults are not explicitly setting clear examples for their children.
Again, you should get a second answer before you answer this.
C hope that helps have a good one
