[单选题]
The energy gap between the valencerqxd a.cmu4/7 and conducti )cppbzhlkb x 6lgm)r(.;s8)von bands in a certain semiconductor is 1.25 es)( .lhgp)m kc;bpvxzb 8r )6lV. What is the threshold wavelength for optical absorption in this substance?
A. $599 \; nm$
B. $959 \; nm$
C. $873 \; nm$
D. $995 \; nm$
