The substance not likely to contain $CaCO_3$ is

Chemical $A$ is used for softening temporary hard water. $A$ reacts with sodium carbonate to produce caustic soda. When $CO_2$ is passed through the solution of $A$,it turns milky. What is the chemical formula of $A$?

An element $X$ with the electronic configuration $1s^2, 2s^2 2p^6, 3s^2$ would be expected to form the chloride with the formula

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 halide of alkaline earth metals is covalent in nature and can be soluble in organic solvent,such as ethanol?

Which are the important ingredients present in Portland cement?