Which of these units would be best to measure the length of our classroom? 1. meters
2. centimeters
3. liters
4. kilometers
5. millimeters

1. meters

Step-by-step 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.