A verb form question tests whether words between commas need a main verb or describe a noun. Find the subject, then sort the forms: a main verb says what it does or is. Past-tense verbs and verbs with helpers can do that; participles, such as -ing and -ed forms, can describe nouns. Next, read through to the period, setting aside extra words between commas. If the subject already has a main verb, another needs a joining word.
Hints
- Hint 1
Look at the end of the study sentence. Which verb there belongs to Lena Ortiz?
- Hint 2
Count the main verbs that belong to Ortiz. If there's already one, does anything join the blank to it as another main verb?
Step-by-step
Sort the forms and count main verbs
Step 1Identify the subject and verb forms
Start with ecologist Lena Ortiz, the subject of the study sentence. We need to know whether the blank is her main verb, which says what she does, or only describes her. Sort the forms: was monitoring and had monitored are main-verb forms, while monitored can serve either job.
- Step 2
Find the main verb after the blank
What does Ortiz do once we read past the words about the lamps? She compared the number of moth visits, so the sentence already has its main verb. No and joins the blank to compared, and no who or that starts a separate part with its own subject and verb. That rules out was monitoring and had monitored, which would each add a second main verb with no joining word.
- Step 3
Run the was test
Could monitored describe Ortiz instead? Use the was test: put was before it and see whether the words mean that something was done to her. “Ortiz was monitored moth activity” doesn't make sense, because Ortiz watches the moth activity; she isn't being watched. Here, monitored would also be a second main verb.
- Step 4
Choose the describing form
The -ing form monitoring describes Ortiz doing the watching. The words moth activity under amber and white lamps tell us what she watches, so the words between the commas add a detail about her work during the study. Choice D.