The lungs are covered by which of the following?

The hand of a man,the wing of a bat,and the flipper of a seal represent:

If $x_n = \cos \frac{\pi}{2^n} + i \sin \frac{\pi}{2^n}$,then $\prod_{n=1}^{\infty} x_n$ is equal to

Match the following components of a cell with their respective percentage of the total cellular mass:

Components	$\%$ of the total cellular mass
$A$. Water	$1$. $10-15$
$B$. Proteins	$2$. $70-90$
$C$. Carbohydrates	$3$. $5-7$
$D$. Lipids	$4$. $3$
$E$. Nucleic acids	$5$. $2$
$F$. Ions	$6$. $1$

Which one of the following is the correct order of the second ionisation potential of $Na, Ne, Mg$ and $Al$?

$A$ ball $A$ of mass $m$ moving along the positive $x$-direction with kinetic energy $K$ and momentum $p$ undergoes an elastic head-on collision with a stationary ball $B$ of mass $M$. After the collision,ball $A$ moves along the negative $x$-direction with kinetic energy $K/9$. The final momentum of ball $B$ is: