A punctuation question about extra information tests whether you can find where the main sentence pauses and starts again. Start near the blank and ask which subject each verb belongs to. Then check how the parts connect: commas can go around extra information, while a semicolon joins complete sentences and a period ends one. No punctuation is needed where words belong together without a break. To check where extra information ends, cross it out and test whether the remaining sentence works.
Hints
- Hint 1
After “have found that,” find what the botanists are describing. Follow that part of the sentence to the verb that tells you what it does.
- Hint 2
Check where the words about an overlooked feature begin and end. How far does that description continue?
- Hint 3
Try the cross-out test on the words beginning with “a feature.” Does the remaining sentence have a subject and a verb that say what the layer does?
Step-by-step
Find the extra information and match its marks
Step 1Follow the root layer to its verb
After have found that, we're reading what the botanists learned about the unusually dense layer of fine roots. Whose verb is have found? It belongs to the botanists, so the layer still needs its own verb. To place the punctuation at the blank, let's follow the words describing that layer.
- Step 2
Separate the descriptions from the layer's verb
The words that the plant develops near the soil surface, describe where the roots grow. Does develops tell what the layer does for the crop? No, it tells what the plant does, and the comma after surface opens extra information we can cross out. The extra information begins a feature often overlooked because most root surveys focus on greater and runs through depths. Inside it, focus belongs to the surveys, so that verb doesn't finish what we're told about the layer either.
- Step 3
Cross out the extra information
Cross out the extra information, from the comma after surface through depths. Does the remaining sentence work? Yes: the unusually dense layer of fine roots that the plant develops near the soil surface helps the crop capture water. Helps belongs to the layer, so the extra information ends right before that verb.
- Step 4
Match the closing mark
Since extra information in the middle must use matching marks, match the comma in surface, a feature with a comma at the other end. Which version completes that pair? The version depths, helps adds the closing comma before the layer's verb. Choice A.