Which of the following ranges of particle size defines the nano scale?

The correct statements about the properties of colloidal solutions are:
$A$. Tyndall effect is used to distinguish between a colloidal solution and a true solution
$B$. Zeta potential is related to movement of colloidal particles
$C$. Brownian motion in colloidal solution is faster if the viscosity of the solution is very high.
$D$. Brownian motion stabilises the sols

The colloidal solution used to treat stomach disorders is

Surface tension of lyophilic sols is

Suspensions are

$A$ colloidal solution is subjected to an electrical field. The particles move towards the anode. The coagulation of the same sol is studied using $NaCl$,$BaCl_2$,and $AlCl_3$ solutions. Their coagulating power should be: