In kinetics, the order of a reaction

a)depends on the rate constant
b)can be deduced from the balanced equation for the reaction
c)must be measured experimentally
d)depends on the concentrations of reactants
e)is the inverse of the entropy of the system

I think it should be C.  You can't always look at the chemical equation of a reaction and tell what order the over all reaction will be.  To do this, you need to preform experiments that have some concentrations held constant while changing others to see how the concentrations affected the rate.  After enough trials with enough concentrations held constant and changed, you will be able to determine the order of each reactant which will give you the order of the overall reaction.

I hope this helps.  Let me know in the comments if anything is unclear.

Nonmetals usually react by gaining electrons