The correct answer is A) become much shorter.
Since the founding of the United States, sentences used in presidential speeches have gradually become much shorter.
The sentences in Presidential speeches in the United States have become much shorter in modern days. One important communication strategy that Press Directors or Public Relations advisers recommend is to deliver the speeches in short, clear and concise ideas in order for the audience to understand better. It has been reflected in the speeches of the President.
The other options of the question were, b) grown increasingly complex, c) started to include more old words, and d) incorporate more Latin words.