In which plant group are the sporophylls arranged spirally along an axis to form distinct compact structures called strobili or cones?

The formula of the product formed when sodium thiosulphate solution is added to silver bromide is:

The $P-V$ diagram of a system undergoing thermodynamic transformation is shown in figure. The work done on the system in going from $A$ $\rightarrow B$ $\rightarrow C$ is $50 \ J$ and $20 \ cal$ heat is given to the system. The change in internal energy between $A$ and $C$ is ...... $J$. (Take $1 \ cal = 4.2 \ J$)

$\begin{aligned} & \frac{x^2+x+1}{(x-1)(x-2)(x-3)}=\frac{A}{x-1}+\frac{B}{x-2}+\frac{C}{x-3} \\ & \Rightarrow A+C= \end{aligned}$

$A$ calcite crystal is placed over a dot on a piece of paper and rotated. On seeing through the calcite,one will see:

$A$ student is allowed to select at most $n$ books from a collection of $(2n + 1)$ books. If the number of ways to select at least one book is $63$,then the value of $n$ is: