Which of the following is $NOT$ a characteristic feature of the class $Mammalia$?

Chemical $A$ is used for water softening to remove temporary hardness. $A$ reacts with sodium carbonate to generate caustic soda. When $CO_2$ is bubbled through $A$,it turns cloudy,what is $A$?

$A$ uniform rod of mass $M$ and length $L$ is placed on a smooth horizontal surface. $A$ horizontal force $F$ is applied at one end of the rod perpendicular to its length. The acceleration of the centre of mass of the rod is:

The relation "congruence modulo $m$" is

Assuming the sun to be a spherical body of radius $R$ at a temperature of $T \ K$,evaluate the total radiant power incident on the earth at a distance $r$ from the sun. (Where $r_0$ is the radius of the earth and $\sigma$ is Stefan's constant.)

The joint equation of two lines passing through the origin,each making an angle of $30^{\circ}$ with the $Y$-axis,is