Answer: "Picking wildflowers while walking through the woods" is a sentence fragment.
Step-by-step explanation: A sentence fragment is an incomplete sentence, that is to say a sentence in which there are important elements missing. In some cases, the main clause is missing, while in other cases the element that has not been included is the main verb or the subject. "Picking wildflowers while walking through the woods" is a sentence fragment because there is no subject. One way of correcting it is writing "I was picking wildflowers while walking through the woods".