A verb form question tests whether the blank needs a main verb and which subject it belongs to. Sort forms by job: -ing, to, and having forms can’t be main verbs alone. Set aside long describing phrases to find the blank’s true subject. Read its clause to the period and count its main verbs; if none is there, the blank needs one. In the simple present, singular subjects take -s and plural subjects don’t.
Hints
- Hint 1
Read from the semicolon to the period. Does the part containing the blank have a main verb of its own?
- Hint 2
Check which words each verb belongs to. What do documenting, depends, and is pulled tell us about?
- Hint 3
Set aside the words between the commas after diagrams. Is the subject left one thing or more than one?
Step-by-step
Sort, count, and match
Step 1Separate the verb forms by job
Sort the verb forms first: having and to forms can’t be main verbs on their own, while the plain present forms can. Which kind does this blank need? Start at her force diagrams, after the semicolon, and read to the period. The semicolon separates two full sentences, so the words after it need their own main verb.
- Step 2
Check where the other verbs belong
Does the part after the semicolon already have a main verb? In recordings documenting the spool’s changing rotation, documenting only describes the recordings. The verb depends belongs to that the direction of acceleration depends, and is pulled belongs to at which the thread is pulled. Those verbs don’t say what the diagrams do, and compares belongs to Mensah before the semicolon. So the blank must be the diagrams’ main verb.
- Step 3
Uncover the true subject
What is the blank’s true subject? Set aside together with a series of high-speed recordings documenting the spool’s changing rotation, the extra information between the commas. Together with adds a detail about the diagrams; it doesn’t join series to the subject the way and would. That leaves her force diagrams, which names more than one diagram, so the subject is plural.
- Step 4
Match the plural subject
Now shrink her force diagrams to they: they show matches, while they shows doesn’t. In the simple present tense, a plural subject takes the form without -s, so plural diagrams take show. Choice C.