$A$ solid reflects incident light and its electrical conductivity decreases with temperature. The binding in this solid is:

Which of the following substances leads to the inhibition of the central nervous system?

$A$ car is moving with a speed of $72 ~km/h$ towards a hill. The car blows its horn at a distance of $1800 ~m$ from the hill. If the echo is heard after $10 ~s$,what is the speed of sound in $m/s$?

The potential difference between $A$ and $B$ in the figure is ................. $V$.

Two blocks of masses $1 ~kg$ and $2 ~kg$ are connected by a metal wire going over a smooth pulley as shown in the figure. The breaking stress of the metal is $2 \times 10^9 ~N/m^2$. What should be the minimum radius of the wire used if it is not to break? Take $g = 10 ~m/s^2$.

Select the correct statement from the following.