Kilometres
Yards if you work in imperial units or metres if you work in metric units
METERS!!!The unit of measurement you would use to measure the width of your classroom is meters.
meter
I would set the ladybird down on a metric ruler and take several photographs as she crawled along it. Later, the photos could be reviewed at my leisure, and her length and width estimated.
Metres
mm
centimetre
cm
It would be millimetres.
Metres, to measure its length or width, square metres to measure its area.
I would go with millimetres
None! I would measure in centimeters if I were you!
Most like a vernier caliper for accurate readings
The metric unit of the meter would be the appropriate measure of the area of classroom. Calculating area involves multiplying the length (in meters) of the classroom's length and width. Area of the classroom would be in square (^2) meters.
Yards if you work in imperial units or metres if you work in metric units
Please specify what you want to measure about the bucket, for example its height, width, circumference, volume, color, albedo, etc.
The width of a pencil would be the metric unit of centimeters