Before the rise of the Mongols in the 13th century, it is now
called central and western Inner Mongolia, particularly the Hetao region,
change back and forth in control between Chinese agriculturalists in the south
and nomadic Mongol of the north. is known through Chinese chronicles and
historians. 
 
        
             
        
        
        
A Tropical monsoon climate<span> (occasionally known as a </span>tropical wet climate<span> or a </span>tropical monsoon and trade-wind littoral climate<span>) is a type of </span>climate<span> that corresponds to the </span>Köppen climate classification<span> category "Am". Tropical monsoon climates have monthly mean temperatures above 18 °C in every month of the year and feature </span>wet<span> and </span>dry<span> seasons, as </span><span>Tropical savanna climates</span>
        
             
        
        
        
I don't really know but I pick b.have always been vestigial.
        
                    
             
        
        
        
It was believed that the magnetic field to be generated deep down in the Earth's core. But the truth is the flow of liquid iron generates electric currents, which produces magnetic fields. 
But the truth is no one really knows for certain so the only thing we know is that the spin of the earth is the cause of its magnetic field
Hope this helped :)
Have a great day