50 !
hese are hints you have to match one on the options with what the hint is describing.

bonsium (bo): this element is important for bone strength, both for aliens and earthlings. it is a metal in group 2 of the periodic table and has 20 neutrons.
spriklium (sk): an atom of this element may have an actual mass of 70 amu with 39 neutrons.
alloyium (am): this is a relatively rare metal that is often used as a hardening agent in metal alloys/mixtures. it is the second lightest metal on the periodic table.
bananium (bn): this element has similar chemical properties to softium and metium, but is heavier than both.

answer options:
be
mg
ca
ar