### Instruction:
Of the following measurements, which units relate to mass? Kilogram, microgram, pound, litre, year, kilometre and ounce.

### Response:
Kilogram (kg), microgram (μg), pound (lb), and ounce (oz) are all units of mass. Kilogram and microgram are units from the metric (SI) system. Pound and ounce are units from the imperial system. Litre is a unit of volume, year is a unit of time and kilometre is a unit of distance.