Answer: The most effective way to vary the length of the sentences in the passage is dividing the sentences into two or three.
Step-by-step explanation: The most effective way to vary the length of the sentences is dividing the sentences that conform the passage into two or three. In that way, by dividing them, most of the compound/complex sentences would be transformed into simple sentences. For example, sentence 4) could be divided into three sentences by writing: "Cromwell served as the chief advocate at the king’s trial and execution. Then, for the next 10 years, he served as chief executive. During that time, he gained a reputation for being a ruthless yet effective leader".