Answer:
-2 
Explanation:
Since its a compound, it's charge is 0. 
So, there are 2 Fe and 3 Oxygen, 
let x = oxidation number of oxygen
2(+3) + 3x =0 
 x =-2 
Side note : even if the oxidation number is positive, make sure to put the positive sign like how you would in numbers 
 
        
             
        
        
        
Answer:
The process of soil formation generally involves the downward movement of clay, water, and dissolved ions, and a common result of that is the development of chemically and texturally different layers known as soil horizons. The typically developed soil horizons, as illustrated in Figure 5.16, are: O — the layer of organic matter A — the layer of partially decayed organic matter mixed with mineral material E— the eluviated (leached) layer from which some of the clay and iron
Explanation:
i'm built different
 
        
             
        
        
        
<span>C. gravity = air resistance</span>