Answer
$mg$.
Work Step by Step
One aspirin tablet is very light, so the appropriate measuring unit is $mg$. That is, one common size of aspirin tablets is 325 $mg$.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.