The applications you have open, and some background processes.
In the Microsoft publisher application (as well as many other websites such as Brainly, Google docs, etc), words underlined in red are spelled incorrectly.
Whether you spelled it incorrectly or did not complete the words, as long as the word is not found in the dictionary, the word would be underlined with a red squiggly line.
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Answer:
Really depends on your situation. If you specified, I'd have an asnwer
