What is a bacteriophage?

If tangents are drawn from any point on the circle $x^2+y^2=25$ to the ellipse $\frac{x^2}{16}+\frac{y^2}{9}=1$,then the angle between the tangents is

The number of Barr bodies in a $XXXX$ female is .....

$A$ family of curves has the differential equation $x y \frac{d y}{d x}=2 y^2-x^2$. Then,the family of curves is

$\int_{-1}^1 \frac{\cosh x}{1+e^{2 x}} d x$ is equal to :

Which kingdoms include decomposers?