sorry for your loss. since she died in 2019 and you're filing for 2020 your filing status is single unless you were (re)married on 12/31/2020 or you can claim widower filing status (if not remarried) if you paid more than 1/2 the cost of a home lived in for more than 1/2 the year by your:
Qualifying Child or
Parent (you must be able to claim the parent as a dependent by they need not live with you if you paid more than 1/2 the cost of keeping up the parent's main home for the entire year) or
Other Qualifying Relative excluding unrelated individuals and individuals that can be claimed as dependents only because of a multiple support agreement.
for stocks and other items you inherited, their tax basis gets adjusted to the value on the date of her death. sale of any stocks inherited automatically get long-term capital gain/loss treatment.
