Adult child as dependent on 2021 return - plus filing status

[PamelaDbq]

I'm getting started with my 2021 taxes.  I'm using TurboxTax Deluxe for Windows, the desktop version. I am a divorced single woman, and my adult son is my dependent. I provide all of his support and he earned zero income. He is 25 and a part time college student. When I enter his information, TurboTax tells me (in RED): "We need you to review some questions about your dependents." 

Because of the red text, I go through the questions again (all looks correct), and get the same red text. If I choose he is "someone else I support," there is no option in the dropdown menu for an adult child. My only option is "other."  Do I need to choose "other" in order to claim my adult son as a dependent?

UPDATE: After typing this question, I went through the dependent stuff for the umpteenth time on TurboTax, and noticed that my son's birthdate was blank. Not sure whether I missed it before or for some reason it did not save. After I entered his birth date, the software give me different questions and apparently that resolved the dependent problem.

Filing status is confusing too.  As I wrote above, I am a divorced single woman who supports one adult child, a part time college student with zero income. The explanations lead me to believe that I would qualify as Head of Household. But TurboTax changes my filing status to Single.  Not sure why this is and if it makes a difference. Any light on these basic questions would be great.

[TomK100]

Based on your description, you should qualify for Head of Household filing status with your son being a qualifying relative.

For the purposes of the Head of Household filing status, a qualifying person is a child, parent, or relative who meets certain conditions, listed below.

The conditions are stricter than those for claiming a dependent; for example, you might be able to claim a roommate as your dependent, but never as a qualifying person for Head of Household status.

A qualifying child would be:

• Your child (including legally adopted), stepchild, foster child, sibling, half-sibling, step-sibling, or a descendant of any of them (for example, your grandchild or niece) AND
• Permanently and totally disabled OR under the age of 19 as of December 31, 2021 (under 24 if a full-time student) and younger than you (or your spouse, if filing jointly) AND
• Lived with you for more than half the year AND
• Single (or if the child is married, you'd have to qualify to claim them as a dependent even if you're not going to claim them as such).

A child that is too old to qualify as a child might be able to qualify as a relative for Head of Household. A qualifying relative would be:

• Your mother or father (including your stepfather or stepmother), if you're qualified to claim them as a dependent (even if you're not claiming them as such) OR
• A relative related by blood, legal adoption, or marriage other than a parent (see the full list of qualifying relatives below) AND lived with you for more than half the year AND that you're able to claim as a dependent (even if you're not claiming them as such).
  • Qualifying relatives:
    • Your brother, sister, half brother, half sister, stepbrother, or stepsister.
    • Your grandparent, or other direct ancestor, but not foster parent.
    • A son or daughter of your brother or sister.
    • A son or daughter of your half brother or half sister.
    • A brother or sister of your father or mother. Your son-in-law, daughter-in-law, father-in-law, mother-in-law, brother-in-law, or sister-in-law.

[Texas Roger]

Regarding why TurboTax is classifying you as single rather than head of household, double check all your answers regarding your child to make sure they are correct. If as a part time college student he lives away from home part of the year, answer that he lived with you the entire year. Part time absences while away at school are considered living with you the entire year.