Which of the following is used in optical fibres?

Which of the following hormones is used to induce callus formation from shoot tips?

The minimum force required to start pushing a body up a rough (frictional coefficient $\mu$) inclined plane is $F_1$,while the minimum force needed to prevent it from sliding down is $F_2$. If the inclined plane makes an angle $\theta$ with the horizontal such that $\tan \theta = 2 \mu$,then the ratio $\frac{F_1}{F_2}$ is:

$\left|\begin{array}{ccc}a-b-c & 2a & 2a \\ 2b & b-c-a & 2b \\ 2c & 2c & c-a-b\end{array}\right|$ is equal to

If $f: R \rightarrow R$ is defined by $f(x)=x-[x]-\frac{1}{2}$ for $x \in R$,where $[x]$ is the greatest integer not exceeding $x$,then $\{x \in R: f(x)=\frac{1}{2}\}$ is equal to :

What type of life cycle in plants is indicated by the given figure?