Which of the following organisms has a cell wall composed of chitin?

What is the objective of Systematics?

Work done in increasing the size of a soap bubble from a radius of $3\, cm$ to $5\, cm$ is nearly (Surface tension of soap solution $= 0.03\, Nm^{-1}$). (in $\pi \,mJ$)

Which one of the following reactions does not occur?

If $\frac{{{{({2^{n + 1}})}^m}({2^{2n}}){2^n}}}{{{{({2^{m + 1}})}^n}{2^{2m}}}} = 1$,then $m =$

$A$ line is at a constant distance $c$ from the origin and meets the coordinate axes in $A$ and $B$. The locus of the centre of the circle passing through $O, A, B$ is