How many wavelengths of $Kr^{86}$ are there in one metre?

The total plane angle subtended by a circle at its centre is ......... $rad$.

Explain this statement clearly: "To call a dimensional quantity 'large' or 'small' is meaningless without specifying a standard for comparison". In view of this,reframe the following statements wherever necessary:
$(a)$ atoms are very small objects
$(b)$ a jet plane moves with great speed
$(c)$ the mass of Jupiter is very large
$(d)$ the air inside this room contains a large number of molecules
$(e)$ a proton is much more massive than an electron
$(f)$ the speed of sound is much smaller than the speed of light.

$1 \, fm = ...... \, m$.

An energy of $13.6 eV$ is equal to

Light year is a unit of