A punctuation question with a description at the end tests whether those words can stand alone. Read across the blank and check whether each side is a complete sentence. Ask whether each verb helps form a complete sentence or sits inside a noun's description beginning with that. Cross out the description to see whether it's extra or needed to finish the thought. A period or semicolon separates complete sentences; a comma sets off extra information, while needed words stay directly joined.
Hints
- Hint 1
Find what the evidence indicates about the rainforest, and check whether that thought is complete before the blank.
- Hint 2
Look for which noun each later verb goes with. Check warn and would irreversibly alter separately.
- Hint 3
Imagine removing the entire description about the scenario. Check whether the sentence still expresses a complete thought without those words.
Step-by-step
Test the final description
Step 1Check the thought before the blank
In Growing evidence from satellite images indicates, indicates is the main verb, the verb that says what the evidence does. For this punctuation question, is the thought complete before the blank? It says the rainforest is approaching a tipping point where tree loss could speed up, so the first part can stand alone.
- Step 2
Find what the later verbs belong to
What happens if we read the ending on its own? In scenario that climatologists warn about, warn belongs to the climatologists, inside the words beginning with that. In one that would irreversibly alter regional weather patterns, the second that gives more detail about one. These verbs sit inside descriptions rather than giving scenario a main verb of its own, so the ending can't stand alone.
- Step 3
Test a sentence break
Could we put a sentence break here? The version with a period would leave the scenario description as a fragment, a group of words that can't stand alone. A semicolon needs a complete sentence on both sides, so the version with a semicolon fails for the same reason. The description has to stay attached.
- Step 4
Attach the extra description
Cross out the description from a scenario through regional weather patterns, and the sentence still works. Those words add extra information the sentence can do without. An extra description at the end takes one comma, and rapidly, a supplies that mark before the description. Choice A.