A. We know that 1 metre = 100 centimetres.

Also 1 centimetre = 10 milimetres.

So, 1 metre = 100 1 centimetre

⇒ 1 metre = 100 10 milimetres

⇒ 1 metre = 1000 milimetres.

B. We know that 1 centimetre = 10 milimetres.

C. We know that 1 kilometre = 1000 metres.

1 metre = 100 centimetre.

1 centimetre = 10 milimetre.

1 kilometre = 1000 1 metre

1 kilometre = 1000 100 1 centimetres

1 kilometre = 1000 100 10 milimetres

1 kilometre = 1000000 milimetres.