MCQ
Which of following is $D$ ?


- A

- ✓

- C

- D







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$(I)\, 1s^2\, 2s^2\, 2p^6\, 3s^2\, 3p^5$
$(II)\, 1s^2\, 2s^2\, 2p^3$
$(III)\, 1s^2\, 2s^2\, 2p^5$
$(IV)\, 1s^2\, 2s^2\, 2p^6\, 3s^2\, 3p^1$

$(1)$ $Fe^{3+}$ gives brown colour with potassium ferricyanide
$(2)$ $Fe^{2+}$ gives blue colour with potassium ferricyanide
$(3)$ $Fe^{3+}$ gives red colour with potassium thiocyanate
$(4)$ $Fe^{2+}$ gives brown colour with ammonium thiocyanate
The total number of methyl $\left(- CH _3\right)$ group($s$) in compound $S$ is. . . .
