c
The ratio of the number of gram atoms among \(C , H , N\) and \(O\) is,

\(C : H : N : O =\frac{20}{12}: \frac{6.67}{1}: \frac{46.67}{14}: \frac{26.66}{16}=1: 4: 2: 1\)

Empirical formula \(= CH _4 N _2 O\). So, empirical weight \(=60 \,g\).

Given, molecular weight \(=60\, g\).

Molecular formula \(=(\text { Empirical formula })_{ n }\)

\(n =\frac{\text { Molecular weight }}{\text { Empirical weight }}=\frac{60}{60}=1\)

So, molecular formula is \(\left( NH _2\right)_2 CO\).