What was the "secondary products revolution" and why was it so important to the spread of agriculture and the growth of cities and states?

Which of the following is an example of proximodistal pattern of growth? (a) abbey learning to sit first before learning to stand or crawl (b) alex learning to move his eyes before learning his first words (c) colin learning to stare at moving objects before trying to touch them with his hands (d) polly learning to grab the objects with her whole hands before learning to pick them up with her fingers