Several candidate Lewis structures can be drawn for the cyanate ion, OCN⁻. Which of the following structures is most plausible based on formal-charge considerations?
a) O=C≡N; all atoms formal charge 0
b) O–−C≡N; –1 formal charge on O
c) O−C≡N–; –1 formal charge on N
d) O=C=N–; –1 formal charge on N