It refers to the part of multicellular organism that are needed for survival and it is considered as the highest level

Ithink 2.2 ibs i think i learned a bit about it

The answer is b because a,c,and d are opinons

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts