[单选题]
A double convex (convex-convex) t:rn33h gug tr5hiniqpa 04wmd lt3ub)ndl 2y5-7v lens has radii of curvature 46 cm, and is made of glass of index of refraction n = 1.60. What is the vlul an3byp id)0 q2td-m57 4wfocal length?
A. infinite
B. $38 \; cm$
C. $30 \; cm$
D. $18 \; cm$
