What are the principal parts of a verb?

Principal Parts of a Verb

The principal parts of a verb are the four forms of the verb from which all forms of the verb can be made. In English the four principal parts are the present (or infinitive), the past tense, the past participle, and the present participle.

Principal Parts of the Verb To Walk:

(to) walk walked walked walking

(To walk is considered a regular verb because we add a -d or -ed to the verb for the past and past participle.)

Principal Parts of the Verb To Run:

(to) run ran run running

(This is considered an irregular verb since one or more of the principal parts is formed in a nonstandard way.)

Since the present participle is always formed by adding -ing to the infinitive, some lists of principal parts omit it.

The answer would be d, coherence.