Why is strontium more reactive than calcium but less reactive than rubidium?

Sr is  below Ca and to the right of Rb in the Periodic Table (see the attached image).

Reactivity increases from top to bottom of a Group. Sr is below Ca, so it is more reactive than Ca.

Reactivity decreases from left to right in a Period. Sr is to the right of Rb, so it is less reactive than Rb.

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .

What are the choices?