Iodine would be your answer!!!
Answer: 
Explanation
Combustion is a chemical reaction in which hydrocarbons are burnt in the presence of oxygen to give carbon dioxide and water.
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
The balanced combustion reaction for butane is,:

The reaction
→
is best classified as double displacement reaction.
Those reaction in which two compounds react by exchanges of ions to form two new compounds is called double displacement reaction. The easiest way to identify double displacement reactions is to check to see whether the cations exchanged anions with each other or not . Always balanced chemical equation is used to determine.
There are three types of double displacement reaction which is given as,
- Precipitation
- Neutralization
- Gas formation
The real world example of double displacement reaction is combining vinegar and baking soda to create homemade volcano.
learn more about double displacement reaction
brainly.com/question/13870042?
#SPJ4
Dang bro that stuff is really hard I’m defiantly on a lower grade lol