Questions

The Earth has four major systems or spheres. These systems are

 1. The geosphere,

 2. The hydrosphere,

 3. The atmosphere, and 

4. The biosphere.

The biosphere is the system where we belong.

When exposed to certain frequencies of radiation, such as radio waves, the subatomic particles called electrons that orbit an atom's nucleus will "jump" back and forth between energy states. Clocks based on this jumping within atoms can therefore provide an extremely precise way to count seconds.It is no surprise then that the international standard for the length of one second is based on atoms. Since 1967, the official definition of a second is 9,192,631,770 cycles of the radiation that gets an atom of the element called caesium to vibrate between two energy states.

‘has’ is incorrectly used since the sentence is in past tense. Moreover, the subject is cities, which is plural.

A man with colour blindness will see red and green as same.