In organic reactions,sodium in liquid ammonia is used as

Guard cells are helpful in:

The differential equation of the family $y=a e^x+b x e^x+c x^2 e^x$ of curves,where $a, b, c$ are arbitrary constants,is

Which of the following is an example of a Gram-positive bacterium?

The angle of elevation of an object on a hill is observed from a certain point in the horizontal plane through its base to be $30^{\circ}$. After walking $120 \ m$ towards it on level ground,the angle of elevation is found to be $60^{\circ}$. The height of the object (in metres) is:

The pole of the straight line $x + 4y = 4$ with respect to the ellipse $x^2 + 4y^2 = 4$ is