[Solved] Which conclusion regarding the presence of siblings for a child is supported by the data collected from a variety of research programs support? A) It is necessary for optimal social and cognitive development. B) It prevents children from becoming selfish and egocentric. C) It threatens a child's sense of emotional security and instrumental competence. D) It has some advantages but is not necessary for successful development. Chalk Formation: A type of limestone characterized by its fine, white, porous structure, formed from the accumulation of microorganisms' calcite shells. Microscopic Organisms: Tiny life forms, not visible to the naked eye, including bacteria, protozoa, and certain types of fungi and algae. Calcium Carbonate: A chemical compound with the formula CaCO3, found in rocks such as limestone, chalk, and marble, and is a major component of shells of marine organisms, snails, and eggs. Chalk Formation: A type of soft, white, porous sedimentary rock composed mainly of calcite or aragonite, formed from the skeletal remains of microorganisms.