Which concept are described in the theory proposed by Hess

Correct Answers are Mid ocean ridges are sites of seafloor spreading and Younger ocean floor is created

Explanation : Hess was a geophysicist. In 1960, he proposed a theory which is later became known as 'Sea Floor Spreading'. Hess discovered that the oceans were shallower in the middle. According to Hess, From Earth's mantle molten material is continuously flowing along the crests of the mid-ocean ridges . As soon as temperature of  magma decreases, it is pushed away from the flanks of the ridges. Due to this process a younger ocean floor is created.Hess also proposed that due to light weight of continental crust, it didn't sink back into the deep earth at trenches as did the oceanic crust.

I would say D

Explanation:

Mid Ocean ridges are sites of seafloor spreading. Not completely sure though.

the results is a decrease in air temperature with an increase of altitude.

explanation:

a.   mass number from atomic number