Answer:
Option B. 2,000 km
Step-by-step explanation:
The scale used shows that the distance between the two cities is 2000 km.
For your understanding, if the scale is 100 km per mm then this means that 1 mm distance on the map is equal to 100 km. If we start measuring the distance between two cities by a straight line then we find that the distance was 20 mm.
Mathematically:
1 mm = 100 km
20 * 1 mm = 100 km * 20
This implies that:
20 mm = 2000 km