"Help rule out" vs. "help to rule out" [duplicate]
Solution 1:
Either an unmarked infinitive (an infinitive without a to complementizer), or a marked infinitive with to will work. Here. Since the matrix verb is help.
But that's only true with help.
Every English verb is has its own rules for what kinds of Object Complement clauses it permits, requires, or forbids. See here for Subject and here for Object Complement examples.
As I used to tell my grammar classes, verbs have more fun.