Which one of the following elements in plants is not remobilised?

Which of the following is a characteristic feature of viruses?

Which of the following is an example of Disciflorae?

The triangle formed by the lines $2x^2+xy-6y^2=0$ and $x+y-1=0$ is

$A$ lens having focal length $f$ and aperture of diameter $d$ forms an image of intensity $I$. If the central region of the lens with diameter $\frac{d}{2}$ is covered by black paper,what will be the new focal length and intensity of the image,respectively?

If $\frac{x-4}{x^2-5x-2k} = \frac{2}{x-2} - \frac{1}{x+k}$,then $k$ is equal to