[单选题]
The energy gap between the valence and condy4:evoqur vgp r (4x1bs45x qu;f,l2 iuction bands in a certain se* eo d+mryg,-xmiconductor is 1.25 eV. What is the threshold wavelength for optiy- *xro +me,gdcal absorption in this substance?
A. $599 \; nm$
B. $959 \; nm$
C. $873 \; nm$
D. $995 \; nm$
