If the lines $4x + 3y - 1 = 0$,$x - y + 5 = 0$,and $kx + 5y - 3 = 0$ are concurrent,then $k$ is equal to:

If $\sin ^{-1}\left(\frac{3}{x}\right)+\sin ^{-1}\left(\frac{4}{x}\right)=\frac{\pi}{2}$,then $x$ is equal to

The protective coat of structural protein in viruses is made up of units called:

$CHO-(CHOH)_4-CH_2OH \xrightarrow{Br_2/H_2O} P$; $P$ is

$A$ conducting rod of length $2l$ is rotating with constant angular speed $\omega$ about its perpendicular bisector. $A$ uniform magnetic field $\vec B$ exists parallel to the axis of rotation. The $e.m.f.$ induced between two ends of the rod is

$DDT$ residues are rapidly passed through the food chain causing biomagnification because $DDT$ is: