The correct options are
A True
D Potassium
In the s-block, reactivity increases as we go down the group because of the increase in the number of shells.
Helium, although a gas, is in the 1st period, Lithium lies in the 2nd period whereas potassium and calcium lie in the 3rd period. Clearly, potassium and calcium are more reactive than lithium and helium. Among calcium and potassium, potassium is more reactive because it only has one electron in its outer most shell unlike calcium which has 2 electrons.
Thus potassium easily reacts to loose that electron and attain noble gas configuration.