Each name is a given number of objects
Answer is A
All elements on the periodic table have a different number of protons that can be represented by its atomic number
It is more likely to be 9 as pH 8 and above are Alkali (Base) and alkali solutions don't tend to react with metals.
Hope this helps :) ~
PV=nRT
Here
P1/T1= P2 / T2
1 torr=133 pascal
600 *133 /215 = 750 *133 / t2
T2= 268.75 K