Tracking the same individuals and collecting data from them at several points over time is called a longitudinal design. This approach lets you watch how outcomes or characteristics change within the same people, and it helps you see how earlier factors relate to later results, capturing the sequence of events. Cross-sectional studies, by contrast, gather data at one moment in time and don’t follow the same people to observe changes, so they can’t reliably establish temporal relationships. Case-control studies start with people who already have or don’t have the outcome and look backward to exposures, not by following subjects forward in time. Experimental designs involve the researcher giving some intervention or treatment and often randomizing participants, which is a different type of study where more control over variables is exercised than in observational longitudinal tracking.

Starch is a plant storage carbohydrate built from glucose units arranged into two polysaccharides: amylose and amylopectin. Amylose is mainly a linear chain of glucose linked by alpha-1,4 bonds, while amylopectin is highly branched, with both alpha-1,4 and alpha-1,6 linkages at the branch points. Together they form the starch molecule, giving it its characteristic structure and digestibility. The other options list monosaccharides or disaccharides (glucose, fructose, galactose, maltose, lactose) rather than the polysaccharide components that make up starch.

Calcium supplements commonly irritate the digestive system. Indigestion (dyspepsia) and other GI upset are typical reactions some people experience, and higher doses or certain formulations can lead to diarrhea. That pattern makes the statement that these side effects are common the best choice. In contrast, saying they have few side effects understates the frequent GI symptoms many users encounter, and claims about never affecting digestion or always causing kidney stones don’t fit what’s commonly observed.

The main idea here is that vitamin K deficiency risk rises when dietary intake is not enough. Vitamin K stores in the body are limited, so regular intake is needed to keep levels adequate. If intake is inadequate, deficiency can develop. The other options aren’t described as direct risk factors in this material— cardiovascular disease, NSAIDs, or age don’t by themselves increase the risk of vitamin K deficiency in the context given.