Atom diameters are sometimes measured in Angstroms. An Angstrom is $1{10}^{-10}m$ in length.

How long is $4\mathrm{.}0$ Angstroms when expressed as nanometers?

q $1\mathrm{.}25$

$0\mathrm{.}004nm$

$0\mathrm{.}40nm$

$400nm$

$40nm$