The 'ing' form used here is 'was swimming' and however, itillustrates the "ing" from of the verb that is commonly used in all these four options verb phrase(in continuous tense), participles(present) and gerund. But the form that has been exemplified as verb phrase i.e. 'was swimming' as it details an action and used with a helping verb. The participles function as adjectives while gerunds function as noun. <em>Thus, the 'ing' form used here is "was swimming" and the correct and most appropriate option would be verb phrase as it illustrates Franklin's action. </em>
