$n_{CO_2}=\dfrac{1,98}{44}=0,045(mol)$
$n_{H_2O}=\dfrac{0,81}{18}=0,045(mol)$
$n_{CO_2}:n_{H_2O}=1:1$
$\Rightarrow$ gluxit có CTTQ $C_n(H_2O)_n$
$n_{\text{gluxit}}=\dfrac{0,045}{n}$
$\Rightarrow M=\dfrac{1,35n}{0,045}=30n$
$n=6\Rightarrow M=180 (C_6H_{12}O_6)$
$\to$ chọn $B$