Answer:
A) to classify and compare properties of elements
Step-by-step explanation:
The modern periodic table displays elements by grouping them into categories, found in the rows and columns of the table.
B does not necessarily fit because allotropes are the varying physical properties some elements display, such as the graphite vs diamond forms of carbon. The periodic table does not display this information.
C does not fit because the periodic table does not explicitly dictate if or how you can make compounds or molecules of the elements listed.
D does not fit because the periodic table lists properties of elements in a way that can help determine the specific element you are looking for. It doesn't necessarily determine whether or not something found is an element or not.