Answer: The solid is a mixture
Step-by-step explanation:
Here's the complete question:
If a solid contains some particles that melt at 50°C and other particles that melt at 110°C, what must be true about the solid?
A. The solid is an element.
B. The solid is a mixture.
C. The solid is a pure substance.
D. The solid has three boiling points.
It should be noted that an element consist of an atom but in this scenario, there are different particles that also have different melting points. Therefore, it's not an element, but rather a mixture.
Also, the solid in this case is not a pure substance and doesn't have three boiling points.
Therefore, the correct option is B.