Question 192·Hard·Form, Structure, and Sense
Overlooked by early astronomers, Neptune was predicted mathematically before it was ever observed, its existence inferred from irregularities in Uranus’s orbit, ______ that mathematics could reveal planets invisible to the naked eye.
Which choice completes the text so that it conforms to the conventions of Standard English?
For questions that ask you to complete a sentence according to Standard English conventions, first decide whether the part before the blank is already a complete sentence. Then look at the punctuation around the blank (comma, period, etc.) to decide if you need a full independent clause, a dependent clause, or a modifier (like an -ing phrase). Finally, check each option for subject–verb agreement and consistent verb tense with the rest of the sentence, eliminating any choice that creates a comma splice, fragment, or awkward, tangled structure.
Hints
Hint 1: Identify whether another full sentence is needed
Read up to the blank and ask yourself: do we already have a complete sentence (subject + verb + complete thought), or are we still waiting for a main verb?
Hint 2: Look at the comma before the blank
The word in the blank comes right after a comma and before the phrase “that mathematics could reveal…”—ask whether that position is more likely to start a new sentence, or to introduce a phrase that describes the result of what came before.
Hint 3: Compare the verb tenses and number
Notice the earlier verbs: was predicted and inferred are past tense and refer to a single event. Eliminate any option whose verb tense or singular/plural form does not fit that established pattern.
Hint 4: Think about -ing forms
On the SAT, when a comma is followed by a word ending in -ing, it often begins a modifying phrase that explains how, why, or with what result something happened. Check if such a phrase would make sense here.
Step-by-step Explanation
Understand the structure of the sentence
Read the sentence without the blank:
Overlooked by early astronomers, Neptune was predicted mathematically before it was ever observed, its existence inferred from irregularities in Uranus’s orbit, ______ that mathematics could reveal planets invisible to the naked eye.
Up to the blank, we already have a full sentence: subject Neptune, verbs was predicted and (was) inferred (in a phrase), and complete information. The words after the blank, “that mathematics could reveal planets invisible to the naked eye,” clearly give a result or conclusion of what came before.
Decide what the blank needs to do grammatically
Because we already have a complete main clause before the blank, we usually do not want to add another full independent clause (that would risk a run-on or awkward structure).
Instead, the blank should introduce a modifying phrase that explains the result of Neptune’s being predicted from Uranus’s orbit—something like “showing that…” or “thereby proving that…”. On the SAT, this kind of result is often expressed with a participial phrase (a phrase starting with a verb ending in -ing).
Check each choice for clause structure, tense, and agreement
Now think about how each type of option would fit after the comma:
- A phrase starting with “and it …” would create another independent clause, which is usually not correct after just a comma.
- A phrase starting with “which …” would be a relative clause and needs a clear noun to refer back to, with matching singular/plural and logical tense.
- A simple past-tense verb (like “demonstrated”) right after the comma would usually act as a second main verb for the same subject, which must fit smoothly with the commas and modifiers already in the sentence.
- A present participle (verb + -ing) can act as a modifier showing a result: “..., ___ing that …”
Keep these roles in mind while you compare them to the actual answer choices.
Match the best grammatical and logical fit
Test each option in the sentence:
- A) and it demonstrates → After a comma, this creates a second independent clause (“it demonstrates …”), making a comma splice. Also, the present tense demonstrates does not match the past time frame set by was predicted and inferred.
- B) which demonstrate → Which needs a plural noun to refer to, but the closest ideas (Neptune’s prediction, its existence) are singular. Also, demonstrate is plural present tense, so it does not agree in number or tense with the sentence.
- C) demonstrated → Placing a simple past verb after a comma and a long modifier (“its existence inferred from …”) makes the sentence structurally awkward: it reads as though Neptune both was predicted and demonstrated in a tangled way. It does not form a clean, standard structure.
- D) demonstrating → This creates a clear participial phrase: “..., demonstrating that mathematics could reveal planets invisible to the naked eye.” It smoothly explains the result of Neptune’s mathematical prediction, matches the past-time context, and correctly modifies the entire preceding idea.
Therefore, the correct answer is D) demonstrating.