When Ca(OH)₂ is added to a beaker of water the solution would turn phenolphthalein pink. Phenolphthalein is a common indicator and is only pink when in basic solutions. By adding calcium hydroxide, you are turning the solution into a basic solution since the concentration of OH⁻ ions is going up and therefore any phenolphthalein in solution would turn pink.
(answers A,C, and D would happen if you added an acid to the water such as HCl)
I hope this helps. Let me know if anything is unclear.