Question

this passage describes a chemical reaction. read the passage. then, follow the instructions below.
the space shuttle program sent astronauts on 135 missions using a fleet of five shuttles between 1981 and 2011. the engines of each shuttle, like other modern rocket engines, used liquid hydrogen as fuel. when liquid hydrogen combines with liquid oxygen, an enormous amount of energy is released, along with water vapor. the shuttles used this energy to launch into space.
complete the sentence.
in this chemical reaction, oxygen is a
reactant product

Explanation:

In a chemical reaction, reactants are the substances that undergo a change. The passage states that "liquid hydrogen combines with liquid oxygen", indicating that both hydrogen and oxygen are taking part in the reaction. Products are the substances formed as a result of the reaction. Here, water vapor is the product. Since oxygen is one of the substances that react (combines) in the chemical reaction described, it is a reactant.

Answer:

reactant