The group 8a (18) elements the group 8a (18) elements melt at high temperatures are good conductors of electricity are unreactive and are rarely found in combination with other elements react vigorously with water are liquids at room temperature

unreactive and are rarely found in combination with other elements

Explanation:

The Group 8A (18) elements are nothing but noble gases. The noble gases in periodic table are Helium, Neon, Argon, krypton,Xenon, Radon. The gases are least reactive elements in the periodic table. The reason being their Octate is complete.

So, option C that is are unreactive and are rarely found in combination with other elements is the correct option. Rest all option are absurd about Group 8A (18) elements

a lot of it means it can be "burned" for energy and sold at one price. if it is scarce, the price will go up

a. are