Final answer:
Of the scenarios provided, Florence texting while waiting for her mother is the best example of multitasking as it involves actively engaging in two tasks simultaneously: communication and waiting.
Step-by-step explanation:
The best example of multitasking among the given scenarios is Florence texting on her phone while waiting for her mother to pick her up from school. This scenario involves actively engaging in two tasks at the same time: communication via texting and waiting for transportation. In contrast, the other scenarios involve passive actions paired with an unconnected activity, such as eating popcorn, crying, or posing for photos, which do not generally require sustained cognitive effort to maintain both activities simultaneously.