Which of the following is/are correct?

$i.1km={10}^{3}m$

$ii.1km={10}^{5}cm$

$iii.1km={10}^{7}mm$

The correct option is B

i and ii

Kilometre is a unit of measuring distance. The word ‘kilo’ means thousand. So, one kilometre = 1000 metres.

$\therefore 1km=1000m={10}^{3}m$

We know that, $1m=100cm$

$\therefore 1km=1000\times 100cm=100000cm={10}^{5}cm$

Also, $1cm=10mm$

$\therefore 1km=100000\times 10mm=1000000mm={10}^{6}mm$

Out of the given options, i and ii are correct.