there is no verb
The principal parts that do not use an auxiliary to form a tense are the base form (infinitive) and the past participle. For example, in the verb "to eat," the principal parts are "eat" (base form) and "eaten" (past participle).
verb Here shopping is an auxuliary verb to the principal verb went.
Eaten is the main verb. Eaten is the past participle of eat.Has is an auxiliary verb.
The principal parts of verbs are typically the base form (infinitive), past tense, past participle, and present participle.
It depends on whether the teacher and the principal are two different individuals or a single individual (which happens in some schools where principal happens also to be an active teacher). If teacher and principal are two separate individuals, then the verb form would be 'are'. If it is the same person who is the teacher and the principal, then the verb should be 'is'. Hope that suffices.
Verb Form
The word formed is a verb. It is the past tense of the verb form.
in English, this is the simple past form.
In the sentence, "Earlier, I helped the principal." the verb is "helped."
The word "dispute" can function as a verb and a noun. As a verb, it refers to a disagreement or argument. As a noun, it is the actual disagreement or argument itself.
"Did" is the irregular past indicative form of the verb "do".
aperire it the third principal part of the verb aperio. It means to open.