What are these answers I am confused

it's filtration, but this is an assumption so my apologies if i got this

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.