A common genetic mutation that lowers levels of the enzyme cathepsin C severely reduces a person's ability to ward of...

David on July 21, 2015

Answers A and E

Answers A and E look very similar. What's the key word or way to differentiate the two? Thanks

2 Replies

Melody on July 23, 2015

Here we have a strengthen with necessary premise question. Remember that a premise is necessary for a conclusion if the falsity of the premise guarantees or brings about the falsity of the conclusion. First we check to see if the answer choice strengthens the passage, and then, if it does strengthen, we negate the answer choice to see if its negation makes the argument fall apart. If the answer choice does both those things then it is our correct answer.

Conclusion: Once researchers develop a way to restore the enzyme to normal levels, we will be able to eliminate periodontitis.

Why? We know that the enzyme cathepsin C destroys diseased cels and eliminates infections. However, a common genetic mutation that lowers levels of the enzyme cathepsin C severely reduces a person's ability to ward off periodontitis.

What's the issue here? The enzyme helps ward off periodontitis. Have we been given any information on whether the enzyme prevents periodontitis, as well? No.

Does answer choice (A) strengthen? No.

Whether or not restoring the enzyme to normal levels is THE ONLY WAY to eliminate periodontitis does nothing to our argument. We need to know whether when enzyme C levels are restored to normal in a person, they will no longer get periodontitis.

Does answer choice (D) strengthen? Yes.

(D) is explicitly telling us that someone whose enzyme levels are restored to normal will not suffer from periodontitis, i.e. periodontitis will be prevented.

Negation: A person whose cathepsin C level has been restored to normal will suffer from periodontitis.

Does the negation make the argument fall apart? Yes.

If someone whose enzyme levels have been restored to normal levels can still get periodontitis, then it no longer stands that bringing the enzyme levels up back to normal will eliminate periodontitis.

Hope that helps! Please let us know if you have any other questions.

Dhishal on August 28 at 01:18AM

Do you mean E instead of D is the correct answer?