Verified Answer :

Circumference of the base of a cylinder:
C = 2 π r = Length of a rectangle ( h - Width )
Answer: B ) 2 π r

For this case the lateral area of the cylinder is given by:
 \(A = 2 * \pi * R * h\)
 Where,
 R: radius of the base of the cylinder
 h: cylinder height
 The length of the rectangle is:
 \(L = \frac{A}{h}\)
 Substituting values:
 \(L = \frac{2 * \pi * R * h}{h}\)
 Simplifying we have:
 \(L = 2 * \pi * R\)
 Answer:
 
B) 2 pi r