[单选题]
A concave spherical mirror has a ewexhfw sk :)9-;1ayjq/w/pw focal len7m+uqorxg7q 6 gth of 20 cm. An object is placed 30 cm xumo+q 6 7qr7gin front of the mirror on the mirror's axis. Where is the image located?
A. 12 cm behind the mirror
B. 12 cm in front of the mirror
C. 60 cm behind the mirror
D. 60 cm in front of the mirror
