Final answer:
In French, the possessive adjective 'leur' is used for singular nouns and 'leurs' for plural nouns to indicate belonging to 'they' or 'them.' The correct options in the provided choices would be either 'leur' (a) for singular or 'leurs' (b or d) for plural, depending on the noun in Sandrine and Martin's statements.
Step-by-step explanation:
The statement 'Sandrine and Martin are talking about their own families and those of their friends' requires the use of possessive adjectives to indicate belonging. In French, possessive adjectives change according to the gender and number of the noun they refer to. The choices provided are a) Leur, b) Leurs, c) Le, and d) Leurs. The correct possessive adjective should match the noun it modifies in both number and gender.
In the English example 'The family packed their suitcases for their vacation,' 'their' is a possessive pronoun. In French, when referring to plural nouns (like 'suitcases' or 'vacations'), we would use 'leurs' which is the plural form of 'leur' and indicates that the belongings are associated with 'they' or 'them' (the family). For singular nouns, 'leur' would be appropriate.