[单选题]
When a person stands 40 cm in ficws8l8cb 0js 8 w266hubpd 0q+kd,vg 5n2. ,-r *b4ryztp+pel(av jqx *wbekront of a cosmetic mirror (concave mirror), the erect image is twice the s*tzv5pyra *xpb., q-(2 kbwerl4j ne+ize of the object. What is the focal length of the mirror?
A. $27 \; cm$
B. $40 \; cm$
C. $80 \; cm$
D. $160 \; cm$
