Which of the following processes can be used to obtain heavy water $(D_2O)$?

Adsorption of phenol from its aqueous solution on to fly ash obeys Freundlich isotherm. At a given temperature, from $10 \ mg \ g ^{-1}$ and $16 \ mg \ g ^{-1}$ aqueous phenol solutions, the concentrations of adsorbed phenol are measured to be $4 \ mg \ g ^{-1}$ and $10 \ mg \ g ^{-1}$, respectively. At this temperature, the concentration (in $mg \ g ^{-1}$ ) of adsorbed phenol from $20 \ mg \ g ^{-1}$ aqueous solution of phenol will be $.....$ .
Use : $\log _{10} 2=0.3$

$A$ particle falls from a height $h$ upon a fixed horizontal plane and rebounds. If $e$ is the coefficient of restitution,the total distance travelled before rebounding has stopped is

Through which cell of the embryo sac does the pollen tube enter the embryo sac?

$A$ parallel plate capacitor has plates with area $A$ and separation $d$. $A$ battery charges the plates to a potential difference $V_0$. The battery is then disconnected and a dielectric slab of thickness $d$ is introduced. The ratio of energy stored in the capacitor before and after the slab is introduced is:

Assertion: The ferromagnetic substance does not obey Curie's law.
Reason: At Curie point, a ferromagnetic substance starts behaving as a paramagnetic substance.