Significant figures in $0.00051$ are

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

Dimensions of pressure are same as that of

Three successive measurements in an experiment gave the values $10.9$,$11.4042$,and $11.42$. The correct way of reporting the average value is

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 $20 \,cm$.

Provide the full forms for the following:
$(i)$ $CGPM$
$(ii)$ $amu$
$(iii)$ $u$