Agroup of words with a subject and verb that does not express a complete thought is called a(n) .

That would be called a Subordinate Clause.

dependent clause  

Explanation :

A group of words with a subject and verb that does not express a complete thought is called a(n) dependent clause.

fire

explanation:

reading poetry is challenging when you don't have or very little of social context and culture schema.

solution: read the introduction, the norm, or even explaination if you still dont get it.