The question is incomplete; the complete question is;
Which pair of properties describes the elements in Group 18?
They are chemically stable and liquid at room temperature.
They have eight valence electrons and are flammable.
They are magnetic and boil at low temperatures.
They are gaseous at room temperature and chemically stable.
Answer:
They are gaseous at room temperature and chemically stable.
Step-by-step explanation:
The group 18 elements are generally called the noble gases or the inert gases. This is because they are mostly monoatomic gases with a high degree of chemical stability.
Recall that group 18 elements already have eight electrons in their outermost shell so they are very stable as a result of a complete octet. They do not easily participate in chemical reactions because of their chemical inertness.