What are $X$ and $Y$ in the following reactions?

The number of points in $(-\infty, \infty)$,for which $x^2-x \sin x-\cos x=0$,is

Which of the following represents a surfactant molecule?

If the circle $x^2+y^2+6x-2y+k=0$ bisects the circumference of the circle $x^2+y^2+2x-6y-15=0$,then $k=$

If the excess pressure inside a soap bubble is balanced by an oil column of height $2\; mm$,then the surface tension of the soap solution will be ($r = 1\; cm$ and density $d = 0.8\; g/cm^3$).

$A$ non-conducting body floats in a liquid at $20^{\circ} C$ with $\frac{2}{3}$ of its volume immersed in the liquid. When the liquid temperature is increased to $100^{\circ} C$,$\frac{3}{4}$ of the body's volume is immersed in the liquid. Then the coefficient of real expansion of the liquid is (neglecting the expansion of the container of the liquid):