The smallest scale of the following is

a 1: 200

b 1: 1000

c. 1: 500

d. 1: 300

B) 1:100

Explanation:

this explanation is actually simple.

you can see this problem as a simple comparation if you move for example

1:10

if you move 1 cm you are going to move 10cm  in the other side usually is used for planes in architecture or sizing issues, so, if the scale need to be grater, that is if is necessary to increase the number inthe right side in this case 10 cm to 100cm it is because in 100 the resolution is better.

you can see this problem as a fraction

1/10 or 1/1000

the answer would be   dignified - apex