$SiCl_4$ on hydrolysis forms $'X'$ and HCl. Compound $'X'$ loses water at $1000^{\circ}$ and gives $'Y'$. Compounds $'X'$ and $'Y'$ respectively are :

$\begin {array} {1 1} (1)\;H_2SiCL_6,SiO_2 & \quad (2)\;H_4S_iO_4,S_i \\ (3)\;SiO_2,S_i & \quad (4)\;H_4SiO_4,SiO_2 \end {array}$

$(4)\;H_4SiO_4,SiO_2$