The number of gram atoms of oxygen present in $0.3$ gram mole of ${\left({CH}_{2}COOH\right)}_2.2H_{2}O$ is

One molecule of oxalic acid dihydrate contains six oxygen atoms. Thus, one mole of oxalic acid dihydrate will contain six moles of oxygen atoms. 

Number of gram atoms $=$ number of moles $\times$ number of oxygen atom.

Number of moles $=0.3$.

Number of oxygen atom $=6$.

So, the number gram atoms $=0.3\times 6=1.8$.

Therefore, option B is correct.