The least count of a stopwatch is $\frac{1}{5} \, s$. The time of $20$ oscillations of a pendulum is measured to be $25 \, s$. The maximum percentage error in the measurement of time will be ..... $\%$

Genes that are involved in turning on or off the transcription of a set of structural genes are called:

Two unknown resistances are connected in two gaps of a meter-bridge. The null point is obtained at $40 \ cm$ from left end. A $30 \Omega$ resistance is connected in series with the smaller of the two resistances, the null point shifts by $20 \ cm$ to the right end. The value of smaller resistance in $\Omega$ is

When bauxite powder is mixed with coke and reacted with nitrogen at $2075 \ K$,carbon monoxide and $X$ are formed. What is the gas formed when $X$ is reacted with water?

$AlCl_3$ is ...

Identify $B$ in the following reaction:
$H_4SiO_4$ $\xrightarrow[1000^{\circ}C]{-2H_2O} A$ $\xrightarrow[\Delta]{\text{Carbon}} B + CO$