A verb form question tests whether the blank needs a main verb or a form that only describes. Sort the forms: a main verb tells what a subject does or is, while an -ing form needs a helper to do that job. Read to the period, setting aside verbs in parts beginning with words like while or that. When a new noun follows a comma, check whether it starts a full sentence, because a comma alone can't join two full sentences.
Hints
- Hint 1
Set aside the opening while part. Who does something in the rest of the sentence, and what do they do?
- Hint 2
Look at how the last part connects: what connects “their images” to the words before it?
- Hint 3
Test the words starting with “their images”. What job do these words do in the sentence as a whole?
Step-by-step
Count the verbs and test the comma
Step 1Separate the verb jobs
The forms are shifting fluidly, has shifted fluidly, and shift fluidly can be main verbs, which tell what a subject does or is. But an -ing form without a helper can't be a main verb. Which job does this sentence need? Let's start after While early documentary photographers sought to present objective truth and count the main verbs, since while makes those opening words depend on the rest.
- Step 2
Find the main subject and verb
Who does something after the opening? modern practitioners frequently incorporate staging gives us practitioners as the subject, so incorporate is their main verb. The form arguing only describes, and can reveal belongs to the words beginning with that. Reading to the period, that provoke viewers to question what they see describes ways, not what practitioners or images do.
- Step 3
Test the new noun after the comma
What joins their images ______ between fact and fiction to the sentence before it? Only a comma appears; there's no joining word such as and or because. Using are shifting fluidly, has shifted fluidly, or shift fluidly would give images a main verb, making this part another full sentence. That's a comma splice, two full sentences joined by only a comma. The new noun needs a describing form instead.
- Step 4
Describe what the images do
The images do the shifting, so an -ing form describes them. The form shifting fluidly creates a noun plus a describing form after the comma: their images shifting fluidly tells how the photographs move between fact and fiction without starting a second full sentence. Choice B.