Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Garrett collected some large rocks from a stream near his home. He measured the rocks on a balance. When he records the mass of the rocks, which units should Garrett use?
kilograms
grams or kilograms.