The types of chemical reactions are combination/synthesis, decomposition, replacement/single replacement, double displacement, and combustion of an organic fuel.
The given question is asking for the letter corresponding to the type of reaction for different chemical reactions. The types of reactions mentioned are combination/synthesis, decomposition, replacement/single replacement, double displacement, and combustion of an organic fuel.
A combination or synthesis reaction occurs when two or more substances combine to form a single product. An example is the reaction between hydrogen and oxygen to form water.
A decomposition reaction occurs when a single compound breaks down into two or more simpler substances. An example is the reaction of hydrogen peroxide decomposing into water and oxygen gas.
A single replacement or replacement reaction occurs when one element replaces another element in a compound. An example is the reaction of zinc with hydrochloric acid to form zinc chloride and hydrogen gas.
A double displacement reaction occurs when the positive ions of two ionic compounds exchange places, forming two new compounds. An example is the reaction of sodium chloride with silver nitrate to form sodium nitrate and silver chloride.
A combustion of an organic fuel reaction occurs when an organic fuel reacts with oxygen to produce carbon dioxide and water. An example is the combustion of methane gas (natural gas) in the presence of oxygen.