People have developed models of the universe for thousands of years. identify two observations that a model of the universe would need to explain in order to be useful

Theory relates to a model in science because it presents the possible paradigms and patterns of the said concept and fact. It explains and elaborates the phenomenon of why it happened, how it happened and the factors that are invovlved in the process. A theory is a possible explanation of certain occurence. 
in addition, any time a scientific theory is challenged, it means it's not a good theory. And this statement is not valid. In theoretical models, they are revisited when there are further studies and discoveries found in a certain area where they can be remodeled and reintegrated instead of disregarding its credibility. Models, theories and paradigms are not challenged but rather encouraged, they are supported in many studies since these theories and models were created in order for us to understand a certain phenomenon but it would likely help the scientific society to be updated in the new forms or spheres of improvement rather than discouragement.   

starchy vegetables are high in carbohydrates.

starchy vegetables contain more carbohydrates than non-starchy vegetables.

explanation:

there are two primary categories of carbohydrates, essentially differentiated on the basis of their carbohydrate content (which is in the form of starch - a complex carbohydrate):

starchy vegetablesnon-starchy vegetables

those vegetables which contain little amounts of starch are termed as non-starchy vegetables, and some examples include: artichokes, broccoli and bean sprouts.

vegetables high in their starch content are distinguished as starchy vegetables, and some examples include: potatoes, chickpeas and corn.

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