Why would researchers use a longitudinal design to study motor development

Group of people could have a very specific challenge having to do with the person or the task - need to watch the same person to see how they change; Ex: some type of physical or cognitive challenge and want to see their progression

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covalent bonding is a form of chemical bonding between two non metallic atoms which is characterized by the sharing of pairs of electrons between atoms and other covalent bonds.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.