Final answer:
The present participle in the sentence is 'talking'. It is formed by adding -ing to the base form of the verb and is used in continuous verb tenses.
Step-by-step explanation:
The present participle(s) in the sentence "I was talking on the phone when she came in" is talking. The present participle is formed by adding -ing to the base form of the verb. In this case, the base form of the verb is "talk" and adding -ing creates the present participle "talking". The present participle is used to create continuous verb tenses and to form the progressive aspect of verbs.
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