Which of the following is dolomite?

What is the purpose of adding gypsum $(CaSO_4 \cdot 2H_2O)$ to cement?

Given below are two statements:
Statement $I$: None of the alkaline earth metal hydroxides dissolve in alkali.
Statement $II$: Solubility of alkaline earth metal hydroxides in water increases down the group.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following alkaline earth metals forms complex salts?

Which of the following elements shows a high tendency to form peroxide?

The following compounds have been arranged in order of their increasing thermal stabilities. Identify the correct order.
$K_2CO_3$ $(I)$
$MgCO_3$ $(II)$
$CaCO_3$ $(III)$
$BeCO_3$ $(IV)$