Answer:
Someone who destroys or damages someone else's property.
Explanation:
When you're unsure about what a word means, you can look it up in a dictionary. A dictionary is an alphabetically arranged listing of words that contains different information about them, such as their definitions, examples, origin, pronunciation, etc.
A saboteur is someone who performs sabotage, i.e. someone who destroys or damages something deliberately. This often involves the destruction of someone else's property.
This is why the second option is the correct one.
