Answer:
The second option is correct!
Explanation:
안녕 내 절친!
Younger than = less than
Less than symbol is = <
People cannot have a negative age, so a must be positive.
Thus, the second option is right!
a < 18 and a must be a positive number
Hope this will help you!
And with lot's and lot's of Luv,
-From your BFF