In humans,which disorder is caused due to the absence of one of the $X$ chromosomes,i.e.,$45$ chromosomes with $XO$ genotype?

Which one of the following statements about packing in solids is incorrect?

The time taken by a photoelectron to come out after the photon strikes is approximately

In polymeric $(BeCl_2)_n$,there are

The temperature of the hot junction of a thermocouple changes from $80\,^{\circ}C$ to $100\,^{\circ}C$. The percentage change in thermoelectric power is ............... $\%$.

$A$ tank with vertical walls is mounted so that its base is at a height $H$ above the horizontal ground. The tank is filled with water to a depth $h$. $A$ hole is punched in the side wall of the tank at a depth $x$ below the water surface. To have maximum range of the emerging stream, the value of $x$ is