[单选题]
The energy gap between the valence and 7/ff bn 1p+yadconduction ba ilm7i mm,(7icnds in a certain semiconductor is 1. (il7,m7m iimc25 eV. What is the threshold wavelength for optical absorption in this substance?
A. $599 \; nm$
B. $959 \; nm$
C. $873 \; nm$
D. $995 \; nm$
