This is a sentence in my grammar book.
He was asked to write the letter.
In the book it says :
He = subject , was asked to write the letter = subject complement.
The verb ask is a catenative verb.(this part wasn't written, I added myself)
And I came across the following two sentences:
The medicine is not warranted to treat a patient's condition.
In this sentence ,I guess the same rule applies,
with to treat a patient's condition being a subject complement,
And verb warrant here is being used as a catenative verb.
Is my understanding right?
A business plan was designed to boost company's revenue.
However,in this sentence,
I am not sure if the infinitive to boost company's revenue can also be a subject complement,
as it seem to be a purpose adjunct, and verb design isn't catenative.
If my understanding is correct, how can the structure of this sentence be explained?