Depending on your countries standard unit of measurement but either feet or meters would be the answer.
Metres or square metres - depending on whether you wanted to measure its linear dimensions or its floor-space (area).
To measure the width of bed, the unit meter can be used. It can also be measured in feet and inches.
Millimetres.
Centimeter
The estimating unit of measurement in question is the millimeter, or mm.
meters
appropriate unit to measure the width of a textbook = ce ntimeters
Centimeter
A centimetre should suffice.
Metres or square metres - depending on whether you wanted to measure its linear dimensions or its floor-space (area).
'Foot' or 'meter'. Your choice, depending on your preference and the audience.
The head or the point of the pin? I would measure the head in millimeters and the point of the pin in micrometers.
I would go with millimetres
To measure the width of bed, the unit meter can be used. It can also be measured in feet and inches.
Centimetre.
Parsecs
Meter is used in finding the width of the blackboard.