Final answer:
Dalton discovered that all compounds are made of elements.
Step-by-step explanation:
In nature, elements rarely occur alone. Instead, they combine to form compounds. A compound is a substance composed of two or more elements joined by chemical bonds. For example, the compound glucose is always composed of the same three elements: carbon, hydrogen, and oxygen.
Dalton discovered that all compounds are made of elements. Elements are substances that cannot be broken down into simpler substances through chemical reactions. Therefore, compounds are composed of these elements.