The major ingredient $(51 \%)$ in Portland cement 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 represents the correct order of solubility in water?

The complex formation tendency of alkaline earth metals decreases down the group because

Which of the following are amphoteric oxides?

Which of the following elements has two electrons in the $Q$ shell in its ground state?