A cold front is the leading edge of a cooler mass of air, replacing at ground level a warmer mass of air, which lies within a fairly sharp surface trough of low pressure.
Answer:
b) sharpening a pencil
Explanation:
If you melt lead, boil water, or dissolve sugar in water, you can return all of them back to their original state. If you sharpen a pencil, you can't reattach the shavings as they were originally.
Being frozen, staying a liquid, becoming ice, and becoming a gas (steam)
They are examples of elements.
