Animals devoid of respiratory,excretory,and circulatory organs are:

Which one of the following represents the correct order of electronegativity?

With a standard rectangular bar magnet of length $l$,breadth $b$ $(b \ll l)$,and magnetic moment $M$,the time period of the magnet in a vibration magnetometer is $4 \ s$. If the magnet is cut normal to its length into four equal pieces,the time period (in seconds) with one of the pieces is:

$A$ tower subtends angles $\alpha, 2 \alpha$ and $3 \alpha$ respectively at points $A, B$ and $C$,all lying on a horizontal line through the foot of the tower. Then $\frac{A B}{B C}$ is equal to:

$A$ balloon is filled with $500 \ m^3$ of helium gas at $27^{\circ}C$ and $1 \ atm$ pressure. What will be the volume of helium at $3^{\circ}C$ and $0.5 \ atm$ pressure in $m^3$?

If $x = \frac{1}{2} \left( \sqrt{3} + \frac{1}{\sqrt{3}} \right)$,then the value of $\frac{\sqrt{x^2 - 1}}{x - \sqrt{x^2 - 1}}$ is equal to