The density of a substance is $4 \, g/cc$ in a system in which the unit of length is $5 \, cm$ and the unit of mass is $20 \, g$. The density of the substance in the $CGS$ system is: (in $units$)

Which of the following represents the fundamental forces of nature?

To determine the Young's modulus of a wire,the formula is $Y = \frac{FL}{A\Delta L}$,where $L$ is the length,$A$ is the area of cross-section of the wire,and $\Delta L$ is the change in length of the wire when stretched with a force $F$. The conversion factor to change the unit of Young's modulus from $CGS$ to $MKS$ system is $x \times 10^{-1} \ N/m^2$. Find the value of $x$.

The distance of a galaxy is of the order of $10^{25} \ m$. Calculate the order of magnitude of time taken by light to reach us from the galaxy.

Of the following quantities,which one has dimensions different from the remaining three?

Names of units of some physical quantities are given in List-$I$ and their dimensional formulae are given in List-$II$. Match the correct pairs in the lists:

$A$. $Pa \cdot s$	$(i)$. $[L^2 T^{-2} K^{-1}]$
$B$. $N \cdot m \cdot K^{-1}$	$(ii)$. $[MLT^{-3} K^{-1}]$
$C$. $J \cdot kg^{-1} \cdot K^{-1}$	$(iii)$. $[ML^{-1} T^{-1}]$
$D$. $W \cdot m^{-1} \cdot K^{-1}$	$(iv)$. $[ML^2 T^{-2} K^{-1}]$