[单选题]
A double convex (convex-convex) thin lens has radii)jaekw80 rf: d of curvature 46 cm, u6-p3cmv0y w-sh6tc m and is made of glass of index of refraction n = 1.60. What is the foct0-s cmv cphu66m3wy -al length?
A. infinite
B. $38 \; cm$
C. $30 \; cm$
D. $18 \; cm$
