The English physician Edward Jenner found that if experimental subjects

Question

The English physician Edward Jenner found that if experimental subjects were deliberately infected with cowpox, which caused only a mild illness, they are immune from smallpox.

Option A
Option B
Option C
Option D
Option E

(This question is from Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)

Solution

Sentence Analysis

  • The English physician Edward Jenner found (Main Subject: Edward Jenner; Main Verb: found)
    • that if experimental subjects were deliberately infected with cowpox, (Dependent clause, an object to the verb ‘found’ – “If” clause within dependent clause – Subject: experimental subjects; Verb: were infected)
      • which caused only a mild illness, (Dependent clause modifying ‘cowpox’ – Subject: which, Verb: caused)
    • they are immune from (Subject of ‘that clause’: they – referring to ‘experimental subjects’; Verb of ‘that clause’: are)

The sentence talks about what Edward Jenner found. He found that by deliberately infecting, experimental subjects can be made immune to smallpox. This finding is presented using a hypothetical construction.

The sentence has the following problems:

  1. Simple present verb tense ‘are’ is incorrect. Since the presented construction is hypothetical (were infected), we need to use ‘would+verb’ construction.
  2. ‘immune from a disease’ is incorrect. ‘immune to a disease’ is the correct version.

However, ‘immune from’ is not always incorrect; rather, it is used quite frequently in other contexts. Read this article to know more about the different between ‘immune from’ and ‘immune to’. In a gist: If you’re immune from something, it cannot reach you. If you’re immune to something, it will not affect you. Since a disease can generally always reach you, you are immune to a disease, not immune from a disease.

Option Analysis

(A) Incorrect. For the errors mentioned above.

(B) Incorrect. For the following reasons:

  1. The use of comma+verbing ‘causing only a mild illness’ indicates that this ‘causing a mild illness’ is a consequence of deliberately infecting the subjects. In this way, the sentence keeps open a possibility that infection with cowpox in other scenarios (when we are not deliberately infecting) can lead to strong illness too. However, this meaning doesn’t seem as logical as saying that cowpox always leads to mild illness.
  2. Simple present verb tense ‘become’ is incorrect. Since the presented construction is hypothetical (were infected), we need to use ‘would+verb’ construction.
  3. Error no. 2 of the original sentence.

(C) Incorrect. Error no. 1 of the original sentence.

(D) Incorrect. For the following reasons:

  1. Problem no. 1 of option B
  2. Error no. 2 of the original sentence
  3. The use of the simple past tense verb ‘became’ indicates a general rule. Did Edward Jenner find a general rule or a possibility? Finding a possibility seems more logical.

(E) Correct.

If you have any doubts regarding any part of this solution, please feel free to ask in the comments section.

About Chiranjeev Singh

An Alumnus of IIM Ahmedabad and with scores of 780 (2017) and 770 (2013) on GMAT and 99.98%ile on CAT, Chiranjeev is one of the most qualified GMAT tutors in India. Chiranjeev has earlier served as Director of Curriculum at e-GMAT. Chiranjeev has been helping students ace GMAT since 2012. He follows a concept-based methodology to teaching GMAT and is very committed to student success. You may contact him for any private GMAT tutoring needs at CJ@GMATwithCJ.com. He conducts online sessions for students across the world.

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