Which of the following absorbs light energy during photosynthesis?

If $P=(0,1,2)$,$Q=(4,-2,1)$,and $O=(0,0,0)$,then $\angle POQ$ is equal to

Let $P(-1, 0)$,$Q(0, 0)$,and $R(3, 3\sqrt{3})$ be three points. Then the equation of the bisector of the angle $\angle PQR$ is

If the change in the value of $g$ at a height $h$ above the surface of the earth is the same as at a depth $x$ below it,then (both $x$ and $h$ being much smaller than the radius of the earth)

The major product of the following reaction is:

What is meant by 'demineralised' water and how can it be obtained?