A ruler
You would use kilograms (kg) to measure someone's mass in metric units.
What metric unit would you use to measure a computer keyboard
Litres
It would probably be miles.
Celsius degrees
What measure of units would you use to measure the thickness of a phone book
To measure a soccer field in the metric system, you would use a metric measuring tape or a measuring wheel. The units used could be meters or centimeters. In the English system, you would use a tape measure or a measuring wheel calibrated in feet or yards. The units used would be feet or yards.
Meters
one page of a phonebook is measured in mm. unit thickness of a phone book is cm
Meters should be used to measure the length of a tennis court in metric units.
Yards if you work in imperial units or metres if you work in metric units
Mass and weight are two different things: you cannot measure the mass of your weight. That is like talking about the temperature of your height - it makes no sense.