Answer:
As the average kinetic energy increases, the particles move faster and collide more frequently per unit time and possess greater energy when they collide. Both of these factors increase the reaction rate. Hence the reaction rate of virtually all reactions increases with increasing temperature
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Since monosaccharides are the simplest units of carbohydrates, then they are made up of carbon, hydrogen, and oxygen atoms.
empirical formula : CxH2xOx
where

Monosaccharides can be classified by the number x of carbon atoms they contain: triose(3) tetrose (4), pentose (5), hexose (6), heptose (7), and so on.
Answer is: three.
Unbalanced chemical reaction: Fe+4H₂O → Fe₃O₄ + 4H₂.
Balanced chemical reaction: 3Fe+4H₂O → Fe₃O₄ + 4H₂.
In balanced reaction, there is three iron atoms on the left and on the right, eight hydrogen atoms and four oxygen atoms on both side of chemical reaction.
I believe a. is the answer.