Changes in $GnRH$ pulse frequency in females is controlled by circulating levels of

On addition of $1 \, mL$ of $10 \% \, NaCl$ solution to $10 \, mL$ gold sol in the presence of $0.25 \, g$ of starch,the coagulation is just prevented. The gold number of starch is:

If work $W$ is done in blowing a bubble of radius $R$ from a soap solution,then the work done in blowing a bubble of radius $2R$ from the same solution is

Which is the best method to conserve the wild relatives of plants?

The period of oscillation of a mass $M$ suspended from a spring of negligible mass is $T$. If along with it another mass $M$ is also suspended,the period of oscillation will now be

$A$ and $B$ are two concentric circular loops carrying currents $i_1$ and $i_2$ as shown in the figure. If the ratio of their radii is $1:2$ and the ratio of the magnetic flux densities at the centre $O$ due to $A$ and $B$ is $1:3$,then the value of $\frac{i_1}{i_2}$ will be