A verb form question with paired actions tests whether linked verbs work together. First, sort the forms: a main verb says what the subject does or is, while an -ing form needs a helper to work as a main verb. Then you find the subject and count its main verbs, checking for words that link another action. Paired actions normally match in form and tense unless time clues differ. A verb takes no comma before the words it acts on.
Hints
- Hint 1
Look at the paired words around the blank: not only and but also. What do they link in this sentence?
- Hint 2
Use designed to check the verb form, then find the added verb's object. The object answers the question: the verb acts on what?
Step-by-step
Find the paired verbs
Step 1Sort the forms and find the subject
Sort the forms: the simple past forms and the version with was can be main verbs, while overseeing alone can't. Who does the work? Architect Julia Morgan is the subject, and designed says what she did. Morgan already has a main verb, so let's check whether the linking words allow another.
- Step 2
Check what the linking words allow
What do not only and but also link? They pair designing buildings with supervising their construction as two things Morgan did. These words allow a second main verb for Morgan, instead of a form that only describes her. Overseeing can't fill that job by itself because an -ing form needs a helper such as was.
- Step 3
Match the past forms
designed uses the simple past, the plain form for a finished past action. Does the text call for a different form in the second half? No, it sums up both kinds of work throughout her career, so the paired verbs should match. Was overseeing instead describes work in progress at a past moment.
- Step 4
Keep the verb attached to its object
After but also, their construction tells us what Morgan oversaw, so it's the verb's object. A verb takes no comma before its object, so we can't split oversaw from their construction. That gives us oversaw their construction personally. Choice D.