Answer:
A- mixture
B- element
C- compound
Step-by-step explanation:
A mixture is composed of two or more substances. Since it is not entirely homogeneous throughout, then it can not melt or boil at a fixed temperature.
An element is any substance that cannot be decomposed into simpler substances by ordinary chemical processes. This describes substance B.
A pure chemical element has a fixed melting and boiling point.
A compound is composed of one or more chemical elements. A compound may be broken down into its components by certain processes.