In my opinion, the answer is D, varying sentence lengths. Meaning that you should have simple, compound, and complex sentences, and vary them. Because you should always have specific examples, not general statements. Cliches should be avoided. And paragraph indentation isn't the crucial element in a paper.
Answer:
Machines have eliminated low-skill jobs because they have done the work the people used to be doing themselves. For example the cotton gin, replaced people having to pluck cotton off of bushes.
Explanation:
Hi,
Edit: First one, B. Second, A.
~Elisabeth