A punctuation question with a side comment tests how extra information fits into a sentence. Read through the blank, then cross out the side comment to see what remains. A semicolon joins full sentences; a colon follows a full sentence and introduces a list or explanation. Use a comma before and between full sentences, but not between verbs sharing a subject. Extra comments need matching commas, dashes, or parentheses at both ends, so check where they start and end.
Hints
- Hint 1
Read the sentence from “a machine-learning program” to the end. Find the verbs that tell what the program does.
- Hint 2
Look for the comment about the field tests. Could you remove those words and leave what the program does unchanged?
- Hint 3
Cross out only the field-test comment, then read what's left. Which words must remain to connect the program’s verbs?
Step-by-step
Cross out the comment and test the link
Step 1Find the program’s two verbs
The text says a machine-learning program distinguishes chainsaws from naturally occurring sounds. What does every choice add? Each adds filters out, giving the program another verb, so the same program does both things. The punctuation must connect these verbs while setting off the comment about the field tests.
- Step 2
Find exactly what can be removed
Which words can we cross out? as field tests have shown is an extra comment that we can remove and still leave a complete sentence. Without it, the program filters out background noise caused by storms and distinguishes chainsaws from naturally occurring sounds. The word and must remain in that sentence, because it connects filters out to distinguishes. If we include and in what we cross out, the program’s two verbs lose their link.
- Step 3
Test the semicolon and colon
Can the words after and stand alone? They include the comment and distinguishes chainsaws, but they still need the program named earlier to say what distinguishes the sounds. A semicolon needs a full sentence on each side, so storms; and can't work. storms: and also breaks the program’s joined verbs rather than introducing a list or an explanation.
- Step 4
Place the opening comma
Where should the comma pair begin? With storms, and as, crossing out the extra comment would leave a machine-learning program with two verbs but no and. The opening comma belongs after and, immediately before as, to match the comma after shown. That gives storms and, as field tests have shown,. Choice A.