Which of the following fiber crops is grown in the largest area in India?

The element with atomic number $12$ belongs to ......... group and ......... period.

In an $ac$ circuit $I = 100 \sin(200 \pi t)$. The time required for the current to achieve its peak value will be

For a crystal,the angle of diffraction $(2 \theta)$ is $90^{\circ}$ and the second order line has a $d$ value of $2.28 \ \mathring{A}$. The wavelength (in $\mathring{A}$) of $X$-rays used for Bragg's diffraction is

The middle lamella is primarily composed of:

Which of the following is responsible for the production of biogas?