Who proposed that all of the present continents were once joined together in a single supercontinent called Pangaea? Select one: a. Alfred Wegener b. Charles Darwin c. Arthur Holmes d. Harry Hess

Alfred Wegener

Explanation:

In 1915, Alfred Wegener, a German geophysicist and meteorologist first developed the concept Pangea. He proposed that the present continents were once fully assembled together about 175 million years ago before it began to break apart. It is believed that a supercontinent existed during the late Paleozoic and early Mesozoic eras. It is also believed that the formation and breakage of the supercontinent have been cyclical through Earth's history.

answer; hypnagogic sensations)

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.