Answer:
1. meters
Explanation:
The smallest unit given in the choice is millimeters. Then comes the centimeters, then meters, and the kilometers.
Liters is used to measure the volume of a liquid. For example we get 1 liters of milk but not 1 kilometers of milk.
The kilometers has a 1000 meters and
1m= 100 cm
1cm = 10mm
The kilometers is quite a large space and usually long distances such as length between 2 towns is measured in kilometers.
The area of the room or length is usually measured in feet but since feet is not given here.
1 feet = 0.3048 m
so the most suitable selection would be meters.
The millimeters is very small. 1 cm has 10 mm. A foot consists of 30.48 cm.
So meters is used.