Answer:
Today, scientists believe that the main reason the earth has had periodic ages is that the climate of earth is controlled by the difference in heating of it's surface by the sun. As for example, the equatorial regions are the warmest as the sun is vertically overhead of those areas and the polar regions where the sun is at the extreme angels are the coldest ones.
Explanation:
When a current flows through coil, magnetic field is produced around the coil which induces emf also known as back emf. When current in the coil is increased, more magnetic field is produced which in turn increases the induced emf.
The principle of resistance training that suggests that muscles should be gradually required to do more than they are used to doing is D. OVERLOAD.
The principle of overload states that a greater than normal stress or load on the body is required for training adaptation to take place.
Overload refers to the amount of load or resistance, providing a greater stress, or load, on the body than it is normally accustomed to in order to increase fitness.
The elements found in the Group 1, or the Alkali Metal Group, have electronic configurations that end in

.This means that they have 1 electron readily available to release in order to achieve a stable state.
When these atoms release the valence electron, they will achieve a stable state. For example, Lithium's stable state will be

and Sodium will be

.
The oxidation state will then be +1.
The answer is C.