Concept:Convert mixed fractions to improper fractions, simplify numerator and denominator separately, then divide the results.Explanation:Simplify the numerator: 187×252.Convert to improper fractions: 187=815 and 252=512.So numerator =815×512.Cancel common factors: =2×13×3=29.Simplify the denominator: 643÷43.643=427, so denominator =427÷43=427×34.Cancel common factors: =19=9.Now divide the two results: 29÷9.=29×91=21.Answer:21 (Option D).