[单选题]
A plano-convex lens isl4yc73lgg w*l9m . oz0.p7pkorsk 4kg to have + kta fpgur);,w(h 3hka focal length of 40 cm. It is made of glass of inde+pg,ua( kwh frk;3)h tx of refraction 1.65. What radius of curvature is required?
A. $13 \; cm$
B. $26 \; cm$
C. $32 \; cm$
D. $36 \; cm$
