A verb form question tests how a verb fits the words around it. Read the whole verb phrase and check its subject and time. Present-tense main verbs use the base form with I, you, or plural subjects, and -s with other singular subjects; past-tense forms show past time. An -ing form needs a helping verb to be a main verb, while infinitive to takes the base form. Don't judge an ending apart from the words it follows.
Hints
- Hint 1
Set aside the opening part about digital cameras and read the part about early photographers. Which words before the blank have started their verb phrase?
- Hint 2
Look at the word immediately before the blank. What verb form follows it in the phrase started by had?
Step-by-step
Read the whole verb phrase
Step 1Find the phrase the blank completes
Read early photographers had to together, apart from the opening part about digital cameras. Who had to do something manually? The subject is early photographers, and had already starts their main verb phrase, the words that say what the subject does or is. The blank completes that phrase rather than starting a separate one.
- Step 2
Use the form that follows “to”
What does had to tell us? The photographers needed to do something, so the to form names what they needed to do. This to form uses the base form, the verb with no added ending. The past time is already shown by had, so we don't add a past-tense ending to the verb after to.
- Step 3
Complete the phrase
Try the choices in had to _____ the exposure time manually for each shot. Adjusting, adjusted, and adjusts each add an ending that this to form doesn't use. Adjust completes the phrase with no added ending and names what the photographers needed to do. Choice C.