The principle of immunization or vaccination is based on the property of ...........

For an ellipse with eccentricity $e = \frac{1}{2}$,the centre is at the origin. If one directrix is $x = 4$,then the equation of the ellipse is

The equations of the tangents to the circle $x^2 + y^2 - 6x + 4y = 12$ which are parallel to the straight line $4x + 3y + 5 = 0$ are:

Which of the following molecules has the maximum dipole moment?

$NaOH$ is prepared by which of the following methods?

Identify $A, B$ and $C$ in the following reactions:
$CH_3 Cl$ $\xrightarrow{KCN} A$ $\xrightarrow{H_3 O^{\oplus}} B$ $\xrightarrow{C_2 H_5 OH / H^{+}, \Delta} C$