Final answer:
It would be best to use grams when finding the mass of a letter since it is usually a lightweight object.
Step-by-step explanation:
When finding the mass of a letter, it would be best to use grams.
A letter is usually a lightweight object, so grams would provide a more suitable unit of measurement.
Grams are commonly used to measure small objects or quantities, and they are a smaller unit compared to kilograms.