I don't know how to explain the structure or rules for this sentence:
"All he could do was look at the diamonds."
I'm sure it has a simple explanation, but these four verbs in a row make it very confusing for one of my students. He wants to know what type of structure it is, with rules that he can use to create similar structures.
Can anyone help?
I was wondering if it would help you if the missing words were replaced:
All that he could do was to look at the diamonds.
Now let's break up the sentence into parts:
All that he could do / was / to look at the diamonds
a. The first part is the complete subject.
i. The simple subject is "all."
ii. "that he could do" is an adjective clause that modifies "all." In other words: the only thing that he could do.
b. The second part is the linking verb. A linking verb is something like an = symbol.
c. The third part is the complement that describes the subject.
Instead of "all," let's use "the only thing." So the sentence reads:
The only thing (that he could do) + was + to look at the diamonds.
That is, "The only thing (that he could do) = to look at the diamonds.
To look at the diamonds = the only thing (that he could do).
So I think that you could tell that student:
The simple subject is the pronoun "all."
"All" is modified by the adjective clause "that he could do."
"Was" is the (linking) verb.
"To look at the diamond" is an infinitive phrase that is the complement of the complete subject ("All that he could do").
"at the diamond" is a prepositional phrase that modifies "to look."