What is the verb in childhood hunger a major problem many parts of world.?

The verb in the sentence "Childhood hunger is a major problem in many parts of the world" is is.

Here's why:

* "is" is the linking verb that connects the subject ("Childhood hunger") to the predicate ("a major problem in many parts of the world").

* It shows a state of being or existence.

Let me know if you have any other sentences you'd like to analyze!