Lactose is a disaccharide of

$[Co(NH_3)Cl(en)_2]^{2+}$ shows two geometrical isomers,$cis$ and $trans$. Which of the following statements is correct?

If the ionic product of water $(K_w)$ is $1.96 \times 10^{-14}$ at $35^{\circ} C$,what is its value at $10^{\circ} C$?

$A$ telescope has an objective lens of focal length $150 \ cm$ and an eyepiece of focal length $5 \ cm$. If a $50 \ m$ tall tower at a distance of $1 \ km$ is observed through this telescope in normal setting,the angle formed by the image of the tower is $\theta$ (in degrees),then $\theta$ is close to..... (in $^{\circ}$)

$\frac{d}{dx}[(1 + x^2)\tan^{-1}x] = $

The variance of $20$ observations is $5$. If each observation is multiplied by $2$,then the new variance of the resulting observations is: