To easily see the rules regarding the Earned Income Credit (EIC), you can refer to a table in IRS Publication 596 Earned Income Credit and IRS Publication 17 Your Federal Income Tax (For Individuals). The table is labeled Earned Income Credit In a Nutshell.
In the 2019 IRS Publication 596, refer to Table 1 on page 2.
In the 2019 IRS Publication 17, refer to Table 35-1 on page 222.