What is the function of Copper-$T$?

Water is considered to be polluted if the dissolved oxygen $(D.O.)$ content is less than ... $ppm$ :

$A$ lead shot of $1\, mm$ diameter falls through a long column of glycerine. The variation of its velocity $v$ with distance covered is represented by

The angle of elevation of an object on a hill is observed from a certain point in the horizontal plane through its base to be $30^{\circ}$. After walking $120 \ m$ towards it on level ground,the angle of elevation is found to be $60^{\circ}$. The height of the object (in metres) is:

In a $500 \ mL$ capacity vessel,$CO$ and $Cl_2$ are mixed to form $COCl_2$. At equilibrium,it contains $0.2 \ mole$ of $COCl_2$ and $0.1 \ mole$ of each of $CO$ and $Cl_2$. The equilibrium constant $K_c$ for the reaction,$CO(g) + Cl_2(g) \rightleftharpoons COCl_2(g)$ is:

$A$ solution of urea (molar mass $60 \ g \ mol^{-1}$) boils at $100.18 \ ^oC$ at atmospheric pressure. If $K_f$ and $K_b$ for water are $1.86$ and $0.512 \ K \ kg \ mol^{-1}$ respectively,the above solution will freeze at ......... $^oC$.