Concept:The perimeter of a rectangle is twice the sum of its length and width.Explanation:Length =x cm and width =(x−1) cm.Perimeter =2(length+width)=16.So 2(x+(x−1))=16.Simplify: 2(2x−1)=16.Divide both sides by 2: 2x−1=8.Therefore 2x=9, so x=29=421 cm.Answer:x=421 cm, which is Option C.