Answer:
B. X= Elements, Y= Compounds
Step-by-step explanation:
An element is a substance that is made up of only one type of atom. The atoms of an element can combine together chemically to form a molecule but can still exist as an individual atom e.g. Hydrogen atom; H can form molecule H2. Since only one atom makes up an element, its electrons act independently.
Compounds, on the other hand, are substances that are made up of more than one type of atom chemically combined. A compound can only exist as a molecule because it always contains more than one atom bonded together. However, since more than one atom are involved in the chemical bond that holds them together, electrons are shared with other atoms. Example of a compound is H20 containing atoms of hydrogen and oxygen that are chemically combined.