Answer:
Cooking; rang.
Explanation:
A verb is one of the parts of speech in English language. Verbs can be defined as any word that describes an action, occurrence, or state of existence. Some examples of verb are dance, sing, walk, play, run, sit, etc.
When a verb is used in its basic form, it is known as its infinitive while when it is used as an adjective or to form tenses, it is known as its participle.
Basically, the present participle of a verb ends with "ing" such as cooking, calling, singing, dancing etc., while its past participle sometimes ends with "ed" such as ringed, loved, talked, singed, etc.
In this scenario, cook should be present participle while ring is past participle.
Hence, she was cooking when the phone rang.