[单选题]
Estimate the observed wavelencml*rumvi ,-*-v l3o;x rppo,gth for the 656 nm line in the6 xv+ we,+ywr0kjk,w l spectrum of a star wre+k ,wyl,v+0kww j6xhich is 100 million light-years from us.
A. $653 \; nm$
B. $656 \; nm$
C. $659 \; nm$
D. $692 \; nm$
