C. Cello playing music at a concert
Answer : The balanced chemical equation is,

Explanation :
Balanced chemical equation : It is defined as the number of atoms of individual elements present on the reactant side must be equal to the number of atoms of individual elements present on product side.
The given unbalanced chemical reaction is,

This chemical reaction is an unbalanced reaction because in this reaction, the number of atoms of individual elements are not balanced.
In order to balanced the chemical reaction, the coefficient 2 is put before the
, the coefficient 3 is put before the
and the coefficient 4 is put before the
.
The energy evolved in this reaction = 
Thus, the balanced chemical reaction will be,

In preparing diluted solutions from concentrated solutions we can use the following formula
c1v1 = c2v2
c1 and v1 are the concentration and volume of the concentrated solution respectively
c2 and v2 are the concentrations and volume of the diluted solution respectively
Substituting these values ,
20 mL x 1.0 M = C x 60 mL
C = 0.33 M
The concentration of the resulting diluted solutions is 0.33 M
The given reaction is a combustion reaction, since a hydrocarbon is burning in presence of oxygen