The sentence that has pronoun agreement is:
D. "When the family saw the storm coming, they decided to take their picnic inside."
How to explain
In this sentence, the plural noun "family" is correctly followed by the plural pronoun "they," maintaining agreement in number between the noun and the pronoun.
In sentence D, the subject is "family," which is a collective noun. While "family" refers to a singular unit, it can represent multiple individuals. In this case, the collective noun "family" is treated as a plural entity, so the pronoun "they" is appropriately used to agree in number with the noun.
This maintains consistency in the sentence structure by employing a plural pronoun to refer to the plural interpretation of the collective noun "family," reflecting proper pronoun agreement.