The molar mass of ${\mathrm{CO}}_2$ is:

The molar mass can be calculated easily by adding the masses of individual elements which make up the compound.

Therefore, the molar mass of carbon dioxide ${\mathrm{CO}}_2$ is as follows;
The atomic mass of carbon + $2\times$(atomic mass of oxygen)

$$\begin{gathered} 12+2\left(16\right) \\ =12+32 \\ =44\text{ amu} \end{gathered}$$

Hence option (B) is correct.