Among the following,the least stable resonance structure is

$\int_2^3 \frac{dx}{x^2-x}$ is equal to

The number of values of $x$ in the interval $[0, 5\pi]$ satisfying the equation $3\sin^2 x - 7\sin x + 2 = 0$ is

Let the relation $R$ be defined on the set of natural numbers $N$ by $a R b$ if $3 a + 2 b = 27$. Then $R$ is:

In angiosperms,the functional megaspore develops into:

If a bar magnet of pole strength $m$ and magnetic moment $M$ is cut equally $5$ times parallel to its axis and again $3$ times perpendicular to its axis,then the pole strength and magnetic moment of each piece are respectively