Which element in Group 18 of the Periodic Table has the highest lonization energy?

all the elements in group 18 are Nobel gases or inert gases . all the elements such as neon , helium, argon etc. ,their outermost shell is completely filled . The noble gases have the largest ionization energies, reflecting their chemical inertness

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

its first and third is your answer i did the qustion the fourth isnt right