$X:C_nH_{2n+1}CH(NH_2)COOH\Leftrightarrow C_{n+2}H_{2n+5}O_2N$
$m:x mol\Rightarrow m_1=m-\frac{18x}{2}=m-9x$$2m:2x mol\Rightarrow m_2=2m-\frac{2.18.2x}{3}=2m-24x$
$\Rightarrow 2(8,1+9x)=14,85+24x\Rightarrow x=0,225 mol$
$2C_{n+2}H_{2n+5}O_2N\rightarrow C_{2n+2}H_{4n+8}O_3N_2+H_2O$
$C_{2n+2}H_{4n+8}O_3N_2\overset{+O_2}{\rightarrow}(2n+2)CO_2+(2n+4)H_2O+N_2$
$0,5x (n+2)x$
$\Rightarrow 0,225(n+2)=\frac{8,1}{18}\Rightarrow n=0\Rightarrow X:H_2NCH_2COOH$
$m=0,225.75=16,875\Rightarrow Chon:A$