d
\(\underset{1\,gm }{ M _2 CO _3}+\underset{\text { Excess }}{2 HCl } \rightarrow \underset{0.02 \text { mole }}{2 MCl }+ H _2 O +\underset{0.01 \text { mole }}{ CO _2}\)

From principle of atomic conservation of carbon atom,

Mole of \(M _2 CO _3 \times 1=\) Mole of \(CO _2 \times 1\)

\(\frac{1 gm }{\text { molar mass of } M _2 CO _3}=0.01 \times 1\)

\(\text { Molar mass of } M _2 CO _3=100\,gm / mole\)