For challenging boundary questions, classify every unit around the blank before evaluating the punctuation. Distinguish independent clauses from appositives and other fragments, then check whether the selected choice correctly handles every boundary rather than only the most obvious one.
Hints
- Hint 1
Classify the added phrase
Determine whether “a result that contradicted Moreno's prediction” is an independent clause or a noun phrase describing the preceding finding.
- Hint 2
Locate the next clause
Identify the subject and verb in the text beginning with “the wax.”
- Hint 3
Account for both boundaries
Look for a choice that correctly introduces the descriptive phrase and also creates an appropriate boundary before the final independent clause.
Step-by-step
- Step 1
Identify the structures
The sentence unit beginning with “By pairing” is complete through “photosynthesis.” The words “a result that contradicted Moreno's prediction” form an appositive noun phrase describing the finding; they do not form an independent clause.
- Step 2
Punctuate the appositive and sentence boundary
A dash can introduce the terminal appositive phrase. After that phrase, a period completes the first sentence, and “Instead,” begins a new sentence containing the independent clause “the wax slowed water loss.”
- Step 3
Check the alternatives
The comma-based choice fails to create a valid boundary before “the wax slowed,” producing a comma splice. A semicolon cannot introduce the fragment “a result that contradicted Moreno's prediction,” and omitting punctuation before that appositive leaves the sentence improperly constructed.