1. The standard deduction for a taxpayer using qualified widow(er) filing status is the same as a taxpayer who files as "Married Filing Jointly status for two years after the year of your spouse's death".

Qualifying Widow (or Qualifying Widower) is a filing status that allows you to retain the benefits of the Married Filing Jointly status for two years after the year of your spouse's death. You must have a dependent child in order to file as a Qualifying Widow or Widower. In fact, the full name of this filing status is actually "Qualifying Widow(er) with a Dependent Child."

2. A widow, whose spouse died in 2019, maintains a home for herself and for a 4-year-old cousin (not a dependent) who lives with her the entire year. The widow files her 2020 return with a filing status of "Married Filling Jointly Status".

Qualifying Widow (or Qualifying Widower) is a filing status that allows you to retain the benefits of the Married Filing Jointly status for two years after the year of your spouse's death. You must have a dependent child in order to file as a Qualifying Widow or Widower. In fact, the full name of this filing status is actually "Qualifying Widow(er) with a Dependent Child."

3. The 2020 taxable income of a 20-year-old dependent with $5,300 of wages, $1,000 of interest income, and good vision, is $ 0.

Generally taxable income is equal to income earned from all sources minus standard deduction of $ 12,400 for the year. Hence his taxable income will become zero.

Hope given answer will sovle your query.