Vascular tissues in flowering plants develop from

Consider two reactions:
$I$. $Zn +$ conc. $HNO_3$ (hot) $\to Zn(NO_3)_2 + X + H_2O$
$II$. $Zn +$ dil. $HNO_3$ (cold) $\to Zn(NO_3)_2 + Y + H_2O$
Compounds $X$ and $Y$ are respectively:

An electromagnetic wave of intensity $1400 ~W/m^2$ falls on a metal surface of area $1.5 ~m^2$ and is completely absorbed by it. Find the force exerted by the beam.

In the adjacent circuit,a voltmeter of internal resistance $R$,when connected across $B$ and $C$,reads $\frac{100}{3} \text{ V}$. Neglecting the internal resistance of the battery,the value of $R$ is

The rate of formation of new organic matter by a rabbit in a grassland is called:

Which of the following is absent in polluted water?