Explain what the term 'allotropes' mean​

Explanation:

The term allotrope refers to one or more physical forms of a chemical element that occurs in the same physical state. Allotropes may show differences in chemical and physical properties. Swedish chemist Jons Jakob Berzelius proposed the concept of allotropy in 1841. The word “allotropy” comes from the Greek word allotropia, which means changeableness.

the answer is learned

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).