I think it will be B. Hope it helps :)
Answer;
d. the specific geometry and types of amino acids in the active site
Explanation;
-Enzymes are highly selective catalysts, meaning that each enzyme only speeds up a specific reaction. The molecules that an enzyme works with are called substrates. The substrates bind to a region on the enzyme called the active site.
-For a substrate to bind to the active site of an enzyme it must fit in the active site and be chemically attracted to it. The shape of an enzyme determines how it works. Enzymes have active sites that substrate molecules (the substances involved in the chemical reaction) fit into when a reaction happens.
The astronomical unit or also know as AU. Scientists use this because it’s convenient and easier to understand! Hope this helps ;)
Answer : The reaction is endothermic.
Explanation :
Formula used :
where,
= change in temperature = 
Q = heat involved in the dissolution of KCl = ?
m = mass = 0.500 + 50.0 = 50.5 g
c = specific heat of resulting solution = 
Now put all the given value in the above formula, we get:
The heat involved in the dissolution of KCl is positive that means as the change in temperature decreases then the reaction is endothermic and as the change in temperature increases then the reaction is exothermic.
Hence, the reaction is endothermic.
