Crotonyl alcohol is an example of

$DNA$ fingerprinting method is very useful for:

The work functions for metals $A, B$ and $C$ are respectively $1.92\, eV, 2.0\, eV$ and $5\, eV$. According to Einstein's photoelectric equation,which of these metals will emit photoelectrons for an incident radiation of wavelength $4100\, \mathring{A}$?

$A$ transformer works on the principle of

The condition that $f(x)=a x^3+b x^2+c x+d$ has no extreme value,is

Let $h(x)$ be differentiable for all $x$ and let $f(x) = (kx + e^x) h(x)$. Where $k$ is some constant. If $h(0) = 5$,$h'(0) = -2$,and $f'(0) = 18$,then the value of $k$ is equal to: