In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with Fe 3+ due to the formation of

1. A. Fe4[Fe(CN)6]3.xH2O
2. B. NaSCN
3. C. [Fe(CN)5NOS] 4-
4. D. [Fe(SCN)] 2+

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