The first operation involved in a Carnot cycle is

Match the following lists:

List-$I$	List-$II$
$(A)$ Benzene	$1$. Phosgene
$(B)$ Ethylene	$2$. Silver mirror
$(C)$ Acetaldehyde	$3$. Mustard gas
$(D)$ Chloroform	$4$. $(4n + 2) \pi$ electrons
	$5$. Carbylamine

The correct matching is:

The locus of the midpoints of the chords of the parabola $y^2 = 4ax$ which pass through the origin is:

Which type of cartilage is found at the ends of long bones?

$A$ wire elongates by $l \, mm$ when a load $W$ is hanged from it. If the wire goes over a pulley and two weights $W$ each are hung at the two ends,the elongation of the wire will be (in $mm$):

$A$ manometer connected to a closed tap reads $4.5 \times 10^5 \, Pa$. When the tap is opened,the reading of the manometer falls to $4 \times 10^5 \, Pa$. The velocity of the flow of water is ........ $m/s$.