The molecular formula of diphenylmethane is $C_{13}H_{12}$. How many structural isomers are possible when one of the hydrogen atoms is replaced by a chlorine atom?

The equation of the parabola with focus $(0, 0)$ and directrix $x + y = 4$ is

Which of the following is an amphoteric hydroxide?

If three unit vectors $\overrightarrow{a}, \overrightarrow{b}, \overrightarrow{c}$ satisfy $\overrightarrow{a}+\overrightarrow{b}+\overrightarrow{c}=\overrightarrow{0}$,then the angle between $\overrightarrow{a}$ and $\overrightarrow{b}$ is

Which of the following reagents will convert propanoic acid to propan-$1$-ol?

$A$ steel wire can withstand a load up to $2940 ~N$. $A$ load of $150 ~kg$ is suspended from a rigid support. The maximum angle through which the wire can be displaced from the mean position,so that the wire does not break when the load passes through the position of equilibrium,is (in $^{\circ}$)