Milk of lime is

Which of the following pairs is chemically dissimilar?

In the alkaline earth metals,the element forming predominantly covalent compounds is

Dead burnt plaster is

Assertion $(A)$: $MgO$,$CaO$,$SrO$,and $BaO$ are insoluble in water.
Reason $(R)$: In aqueous medium,the basic strength of $MgO$,$CaO$,$SrO$,and $BaO$ increases with an increase in the atomic number of the metal.
The correct option among the following is:

Which of the following elements can be represented by the electronic configuration $[Kr]\,5s^2$?