[单选题]
The energy gap between the valence and conduction bands in a cerss.yl;7 tcpo 0taind*o ks,9u+w ipxa 0l;k semiconductor is 1.25 eV. What is the threshold waveleng+o ;*x,aiskkl up9wd0 th for optical absorption in this substance?
A. $599 \; nm$
B. $959 \; nm$
C. $873 \; nm$
D. $995 \; nm$
