Answer
Strange.
Work Step by Step
Use the values in the table to write conditionals. The conditional that can be written using data in the fourth column is:
If a quark has rest energy of 540 MeV and an electric charge of $-\frac{1}{3}$e, then its flavor is Strange.
The characteristics of the given quark match the hypothesis of this conditional , so we can conclude the quark's flavor is Strange.
