A.
3级光谱与4级光谱分开;The spectrum of grade 3 is separated from that of grade 4;
B.
以上都不对;None of the above is true;
C.
1级光谱与2级光谱分开;The spectrum of grade 1 is separated from that of grade 2;
D.
2级光谱与3级光谱分开;Level 2 spectrum is separated from level 3 spectrum;