I apologize for asking too many of these questions, but I need to know for sure if I'm doing this right.

"Thus the creation of infinite universes from this world of nothing was prevented."

I'm confused if it is was or were again.
When I say it to myself, I think 'was' sounds better but I don't know if it's grammatically correct since 'infinite universes' is more than one thing? Then it should be were then?

Subjects must agree with their verb. I taught my students to put parentheses around prepositional phrases to help find the subjects.

"Thus the creation (of infinite universes) (from this world) (of nothing) was prevented."

That makes it clear what the subject and correct verb are.

No need to apologize! I'm here to help.

In this sentence, the correct verb to use is "was." Although "infinite universes" refers to multiple things, the usage of "was" is appropriate because it is being treated as a single concept or a collective noun.

To explain further, when you have a subject that represents a group or collection of things (e.g., "infinite universes"), sometimes the verb can be singular if we are considering the group as a whole. In this case, "infinite universes" is being considered as a single entity or concept, and the verb "was" (singular) is used to match it.

For example, think of the sentence: "The herd of elephants was moving slowly." Here, "herd" is a singular subject, but it represents a group of elephants. Similarly, "infinite universes" is a singular idea representing multiple universes, so "was" is the appropriate choice in your sentence.

It is important to note that verb agreement with collective nouns can be a bit tricky, and sometimes it can depend on the intent and context of the sentence. But in this specific case, "was" is grammatically correct.