what does this quote mean by Ella baker that in order to see where we are going, we not only must remember were we have been, but we must understand where we have been

Ineed someone to describe what they mean in the instructions !

Need asap ! 1. someone at a party has just told a joke, and the photo shows a guest laughing uproariously with his head back, eyes closed, and mouth open. 2. photo of collection of vintage corvette convertibles at an automobile show. stock photography 3. photo of a mosquito filling the entire frame of the photo. 4. photo of the quilt-like appearance of grain fields taken during a ride in a hot-air balloon. 5. photo of the pollution of discarded cans, bottles, and other waste on a beach. 6. photo of the eiffel tower in paris, france. environmental photography aerial photography macro photography documentary photography stock photography candid photography

According to the hierarchy of chords, fill in the missing chord in this progression. i - iv - - i?