element in which of the following groups can exist as a gas at room temperature?

           A) Metals

           B) Nonmetals

           C) Metalloids

           D) All of the above

elements has the largest electron affinity?

           A) Oxygen

           B) Sulfur

           C) Selenium

           D) Tellurium

isotopes of oxygen has nine neutrons?

           A) 16O

           B) 17O

           C) 18O

           D) None of the above

elements has the smallest atomic radius?

           A) Potassium

           B) Calcium

           C) Gallium

           D) Bromine