Minus sign in double quotes in grep is recognized like an option

Question

If I'm writing

grep -v "-NO" file

it says

grep: invalid option -- 'N'

So I need to write grep -v -- "-NO" file or grep -v "\-NO" file.

But why it recognizes the - as option if it is in double quotes?

Answer 1

The quotes are removed by the shell before the arguments are passed to grep, in a step called Quote Removal. Also see Simple Command Expansion. So, really, grep never sees these quotes.