All of the following nondependent taxpayers are U$.$S$.$ citizens. Which is$/$are required to file a $2023$ income tax return?

Calvin $(40),$ qualifying surviving spouse $($QSS$),$ $$26,100$ gross income.

Jen $(68),$ single $($S$),$ $$15,000$ gross income, all from wages.

Sheldon $(67)$ and Ruby $(61),$ married filing jointly $($MFJ$),$ $$28,500$ gross income.

Zachery $(38),$ head of household $($HOH$),$ $$21,350$ gross income.