The following taxpayers are covered by an employer$-$sponsored retirement plan. Which one may FULLY DEDUCT their traditional IRA contribution?

Kelli files single. Her modified AGI is $$68,000.$

Mark files head of household. His modified AGI is $$68,001.$

Samantha is married, did not live with her spouse at any time during the year, and chooses to file a separate return. Her modified AGI is $$10,975.$

Donald is married and files a joint return. Both he and his spouse are covered by an employer$-$sponsored plan. The couple's modified AGI is $$109,500.$