B. were formed make up the verb phrase.
A verb phrase is a phrase composed of verbs, whether the verbs be an action verb or a linking verb.
Writers use action verbs to depict action. They use linking verbs to describe conditions. However, there are instances when action and condition happens at the same time; thus, verb phrases are made.
In the verb phrase "were formed", were is the linking verb describing condition while formed is an action verb.
