One fermi is $....$ (in $cm$).

The density of the solution is $2.15 \ g \ mL^{-1}$,then the mass of $2.5 \ mL$ solution in correct significant figures is $........ \ g$.

What is the $SI$ unit of luminous intensity?

Match the units in Column-$A$ with their equivalent values in Column-$B$ and select the correct option:

Column-$A$	Column-$B$
$1$. Femtometer	$(P)$. $10^{-3} \ \mu m$
$2$. Picometer	$(Q)$. $10^{-3} \ mm$
$3$. Nanometer	$(R)$. $10^{-3} \ pm$
$4$. Micrometer	$(S)$. $10^{-3} \ cm$
	$(W)$. $10^{-3} \ nm$

If the diameter of a carbon atom is $0.15 \,nm$,calculate the number of carbon atoms which can be placed side by side in a straight line across the length of a scale of length $20 \,cm$.

Consider the following:
$A) 0.0025$
$B) 500.0$
$C) 2.0034$
Number of significant figures in $A, B$ and $C$ respectively,are