Answer:
The answer is D. It doesn't have too many commas and flows smoothly.
The correct answer is parenthesis. A parenthesis normally appears in sentences when extra information unrelated to the main idea of the sentence is inserted. The trick in knowing if a phrase can be included in a parenthesis is when you take it out and the idea of the sentence is intact.
If your choices are the following:
A. Both isolation and omnipotence are impossible to achieve.
B. The United States will someday be able to balance isolation and omnipotence.
C. It was inevitable that omnipotence would replace isolation.
D. The United States missed a chance to be separate from Europe.
Then the answer is A.
A because you should tell what the paragraph is about, provide evidence to support your topic, and explain how the evidence supports your topic.
