Which of the following characteristics is inconsistent with viroids?

If $b+c=3a$,then $\cot \frac{B}{2} \cot \frac{C}{2}$ is equal to :

The values of a function $f(x)$ at different values of $x$ are given in the table below:

$x$	$0$	$1$	$2$	$3$	$4$	$5$
$f(x)$	$2$	$3$	$6$	$11$	$18$	$27$

Then,the approximate area (in square units) bounded by the curve $y=f(x)$ and the $x$-axis between $x=0$ and $x=5$,using the Trapezoidal rule,is

The diameters of a circle are along $2x+y-7=0$ and $x+3y-11=0$. Then,the equation of this circle,which also passes through $(5,7)$,is

Two thick wires and two thin wires,all of the same material and same length,form a square in three different ways $P$,$Q$,and $R$ as shown in the figure. With the current connection shown,the magnetic field at the centre of the square is zero in which cases?

Which property of the alkaline earth metals increases with their atomic number?