In which type of reaction do two or more substances combine to produce a single substance?
(1) synthesis
(2) decomposition
(3) single replacement
(4) double replacement

The correct answer is (1) Synthesis

Explanation:

In chemistry, synthesis reaction occurs as two or more substance combine and form a single and complex product, due to this, synthesis reaction is also known as a direct combination, because different to decomposition or replacement reactions the final product includes the substances that were combined. For example, water (H2O) is formed through synthesis by mixing two atoms of hydrogen (H2) and one of Oxygen (H) which means the substances combined form a single substance. Thus, the type of reaction described is Synthesis reaction.