Question

By 1999, astronomers had discovered 17 nearby stars that are orbited by planets about the size of Jupiter

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 complete question can be viewed on GMATClub)

Solution

Meaning Analysis

• By 1999,
• astronomers had discovered 17 nearby stars
  • that are orbited by planets
    • about the size of Jupiter

The sentence says that by a particular time i.e. 1999, astronomers had discovered something. What had they discovered? 17 nearby stars that are orbited by planets, which are about the size of Jupiter

Error Analysis

The sentence is correct in all respects. The use of past perfect “had discovered” is correct since this event was completed before another event i.e. 1999. Besides, the use of present tense “are” in “that are orbited” is correct since this information is true even now i.e. the stars are still orbited by these planets.

Option Analysis

(A) Correct. As discussed above.

(B)  Incorrect. For the below reasons:

1. The closest noun to the relative clause “that were about the size..” is “them”, which refers to stars. The relative pronoun “that” can, however, also refer to planets since “orbiting them” is an essential modifier, and pronouns can jump over essential modifiers. So, we have two antecedents for “that”, and logically, it can refer to either. Therefore, we have pronoun ambiguity in this option.
2. The use of past tense “were” indicates that the stars/planets were about the size of Jupiter in the past but are probably not so now. It is highly improbable (one doesn’t expect the relative sizes of planets or stars to change over the years)

(C) Incorrect. For the below reason:

The use of past tense “were orbited” doesn’t make sense since the stars should still be orbited by the planets. To present such a general fact, we should use simple present “are orbited”. Similarly, the use of the simple past “there were 17 stars” doesn’t make a lot of sense since this is also a general fact.

(D) Incorrect. For the below reasons:

1. The use of present perfect “have discovered” is incorrect since we referring to an event completed before a particular time i.e. 1999.
2. The antecedent for “that” is ambiguous, as explained in explanation for option B.

(E)  Incorrect. For the below reasons:

1. Use of present perfect – Same error as in option D