1. how many mm fit into one km? [a] 103m [b] 10-3m [c] 105m [d] 10-5m [e] none of the above

[a] 103m (I guess that it is 10^3 m)

Explanation:

To calculate how many millimeters you enter in a kilometer, just know the relationship between both units of distance.

The relationship is as follows:

1 km = 1 000 000 mm

So:

1 km = 1000 m = 10^3 m = 10^6 mm = 1 000 000 mm