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.
The answer is B. Controlling Trade. I have taken the test. Tip: Try to talk more formally it is more beneficial, and if you could speak more formal, you would be able to be understood better.