The verb shows the action the subject is the doer of the action eg
The dog chased the cat.
The dog (subject ) chased (verb - action)
"Sat" is a verb, but it is not an action verb. It is a linking verb that connects the subject (the doer of the action) to the subject complement (describes or renames the subject).
"Take" can be both a linking verb and an action verb depending on the context. As a linking verb, it connects the subject to a subject complement that describes or renames the subject. As an action verb, it describes a physical or mental action that the subject is performing.
"Go" can function as both an action verb and a linking verb. As an action verb, it indicates physical movement. As a linking verb, it connects the subject to a subject complement that describes or renames the subject.
The word "looks" can function as both a linking verb and an action verb, depending on how it is used in the sentence. As a linking verb, it connects the subject with a subject complement and describes a state of being. As an action verb, it describes the physical act of directing one's gaze.
The word "grows" can function as both a linking verb and an action verb. When used as a linking verb, it connects the subject to a subject complement that describes or renames it. When used as an action verb, it describes the physical process of increasing in size or developing.
Is is the verb in your sentence.
"Was" is a linking verb. It is used to connect the subject of a sentence to a subject complement that describes or renames the subject.
"Became" can function as both an action verb and a linking verb. As an action verb, it indicates a physical or mental change that occurs. As a linking verb, it connects the subject to a subject complement that describes or renames the subject.
Action verbs show an action taken by the subject, while linking verbs connect the subject to a word that describes or renames it. Example of an action verb: "She ran." Example of a linking verb: "He is happy."
"Leads" can function as either an action verb or a linking verb, depending on the context. As an action verb, it indicates physical or mental action. As a linking verb, it connects the subject to a subject complement that further describes or renames it.
"Felt" can function as either a linking verb or an action verb, depending on its context. When used as a linking verb, it connects the subject of the sentence with a subject complement that describes or renames it (e.g., "I felt tired"). When used as an action verb, it describes a physical or mental sensation experienced by the subject (e.g., "I felt the soft fabric").
"Think" can be used as both an action verb and a linking verb. When used as an action verb, it shows an action being performed (e.g., "I think about it"). When used as a linking verb, it connects the subject with a subject complement that describes or identifies the subject (e.g., "I am thinking clearly").